What about the 'Throw Logan into the fire choice Natasha got pissed at Freddy for'? Perfect example of a moment where Freddy having a higher diplo score would benefit the players. Or the fact Freddy ignored everyone, but the Northern Empire provinces, caused problems? The players are now very political minded and are aware they can exploit Freddy's prestige, they didn't before because they feared Freddy would screw things up.
Yet, the players will go out of their way to avoid being hated. If something happens as a side effect of chosen actions, players will put a bandage on the problem and walk it off. Unless the production of engineering goods is threatened by a dwarf grudge, then the players will do almost (Anna was delayed from going South by 1 extra year, that cost us wonders dreamt by man, apparently for Natasha's peace of mind) anything to permanently fix the problem no matter the cost. The players avoid Adolf, so they can exploit Talabecland later. Marienburg intrigue is going unfought.
No, caring about the diplomatic impact of Freddy's diplo score is a hinderance players use to deny doing any political actions that try to do good willingly beyond player benefit, because people/persons in-game will potentially hate him for it, and players will not accept loss of 'easy win'. The only reason Freddy did good with the prince of Caledor, is because the players had no control over Freddy, and the vampire war showed Ostland has an Arcane Fulcrum. There was one point with Hochland where Freddy tried to do good, but apparently that was for calculated political reasons 'because Magnus said so'. Or what about the MM point where the players refused a duel to settle the issue like Ulricans, and traditional Northerners?
Freddy already had an Average Diplomacy rating when the decision was made to make the choice about Logan instead of letting Natasha do it. If anything? The Logan decision is a demonstration that stats aren't everything.
And before the Vampire War, Freddy was on good terms with Talabecland. Likewise, while we extended the Olive Branch to Victor Ludenhof at the Emperor's request, that wasn't the only time we tried to help Hochland(turn 8, Screw Ludenhof Martial action, turn 9 Bypassing the Asshole diplomatic action, though I personally didn't want the latter one given that Victor Ludenhof was dying), were managing good relations with the Mootland(despite it earning us the scorn of Stirland), didn't have much of an issue with Winkler(which is why Marienburg replaced her with Kaufman) and we were getting along with Middenland until Gunthar usurped Karl Todbringer through what turned out to be a vampire-assisted plot. We also helped Wissenland by sending troops to help out at the Battle of Nuln(despite the fact that Nuln tried to make us limit gunpowder investments when the Wolfenburg school got recognized for the sake of cornering the market) and helped Stirland with their Sylvania issue(despite them disliking us for our friendship with the Moot).
Sure, we hadn't done much with Averland or Reikland(which are damn near on the other side of the Empire) but to say we only focused on the North is inaccurate.
Trying to be diplomatic towards Natasha was only part of the reason for delaying Anna. Another was security concerns with regards to the Dwarves given that the Engineers had
just called their Grudge and we didn't know whether or not they'd try anything. And trying to make Anna happy resulted in people voting to
not force her to travel with a bigger bodyguard. All three of those? Trying to take the feelings of others into account.
That fiasco can be attributed to Freddy trying to avoid another incident with the Dwarves(i.e. trying to be diplomatic), trying to keep our wife from having an aneurysm(diplomacy) and trying to apologize to our daughter by letting her stick to her planning(diplomacy). A less diplomatic Freddy probably would've forced Anna to take extra bodyguards and maybe take a vacation with Natasha before calling it a day.
That, or he wouldn't have greeded for Tilean shinies, refused Anna outright and disciplined her if she stole from the treasury.
As for Fuerbach...
Adolf has not forgiven you, and never will. His sons are of similar mind, but their anger is dull compared to the sharpness of his hatred.
or perhaps even the younger Fuerbach.
When even Magnus the Pious says Fuerbach the Elder won't forgive us and that we should try with his heir? The diplomatic thing to do is to give Adolf Fuerbach space, not to get in his face for the sake of opening relations again beyond their current levels.
Sure, players didn't take Fuerbach's opinion into account during the Vampire War when we didn't stop Johanna from accepting the Blood Kiss(respecting her Agency as we should have with Natasha and Logan apparently). And sure, knighting Urgdug instead of immediately sending letters of thanks was a stupid move that cost us a point of Adolf's opinion. But I doubt people would've voted to suggest to our friend that she should roll over and die and while I may have voted to send the letters over promoting Urgdug, I don't think there are a lot of regrets about knighting Urgdug given how much help he's been so far.
And if making deals with Talabecland after Fuerbach is exploitative? Than, by definition, all our other diplomatic relationships must be exploitative. Kislev? We exploit the fact that they are a buffer state while exploiting their need for Lumber to make gold and exploiting our proximity and Royal Marriage to export guns. Nordland and Ostermark? We're exploiting our friendship to sell them guns. The Moot? We were just using them to get Farming expertise. Those nice letters we sent to Wissenland's newest elector? A fib to isolate the Nuln gunnery school. Asking Alberich for advice after getting on good terms with him already and not voting for his candidate? Clearly a plot to raise his opinion of us further by making him laugh.

More seriously, just because we try to be productive when interacting with other provinces doesn't mean the exchange is one-sided. A trade agreement with Talabecland is going to cause gold to flow into Talabeclander pockets just as surely as it causes gold to flow into Ostlander pockets. Calling it exploitation in this context is pretty inaccurate.
We already apologized to Talabecland, already paid reparations in full and even went so far as to send mercenaries to help save his province. If he wants to deal with us again? He can be the one to make contact. Until then? Assume his previous position of wanting nothing to do with Ostland is still true. Instead of being Greedy for Talabeclander shinies, just leave the man be.
Wait for one of his sons to take over. Or until Freddy dies. Either/or.
With regards to the Marienburg intrigue war, we already spooked their agents once so it didn't exactly go unfought. Nor did you vote for it on turns 28 or 29. Sure, people decided to check up on Hochland and to hunt down our Rogue engineers. So what?
Unless you're saying we should've solved this diplomatically? For example by writing in the recruitment of some Marienburger consultant or something so Marienburg gets to keep their precious monopoly on Asur trade that the Asur didn't care to other with when they rented the Arcane Fulcrum?
Speaking of which, the Caledorian prince was snubbed before we discovered the Arcane Fulcrum and there
was a vote to let the players affect the outcome. So to say we had no control over it or to attribute it going well to the Fulcrum is wrong. It went well because the guy was an asshole whose behaviour was hindering Teclis' plans.
And if we only cared about player benefit, we wouldn't have paid Talabecland their war reparations, wouldn't have offered to take in Moro's family, wouldn't have bothered helping with shit like Sylvania, probably would. Freddy is a Hero of the Empire
because he was willing to sacrifice time, lives and money helping the Empire.
Hell, our diplomacy option on turn 7 was even called "Good Over Profit" where we chose to take a hit to trade income just to help Nordland recover faster. Which is a pretty solid example of "doing good willingly beyond player benefit."
Likewise, while we could've wrestled Gunthar in a calculated political gambit to get the entirety of the Middle Mountains but we ultimately decided that Gunthar's proposal was reasonable since it got us space for our population to flee to in case Ostland gets overrun again and since more Imperial troops just means the place is safer unless something stupid happens to cause war between Ostland and Middenland.