The Lunar die-cap and their number of Charms are meaningless metrics to gauge the competency of the splat, because the question has never been whether they can throw as many dice as Solars, but will they be able to rack up as many successes as quickly and with an equal or fewer amount of investment towards doing so. Because for all Exalted likes to posture about increasing die pools and rolling a bunch of dice, most of those results don't mean a thing unless they Hit, and things won't Hit unless you buy into the things which allow you too. If anything, the concession to make the Lunar cap more like the Solar one speaks to an overall homogenization of the mechanics they are working with, as though they don't imagine they can make something work and be comparably powerful as an outlandishly-inflated Solar die-pool.
For the sake of argument, let us assume a maxed-out normal pool here, 23 dice discounting equipment or external bonuses, Solar and Lunar alike. Rolling this many dice on average, anything at 5 successes or below might as well be a given, automatic pass, and anything above 12 successes is a 50% which rapidly diminishes at ~10% toward automatic-failure for each additional success above that. Which gives us a flexible area between 6 and 11 success where there's a spectrum of possible results:
97% Chance to hit DV 6
94% Chance to hit DV 7
89% Chance to hit DV 8
82% Chance to hit DV 9
72% Chance to hit DV 10
60% Chance to hit DV 11
In 1e, Lunars had no adders whatsoever, but instead their own dice trick of converting Dice from a roll into Successes post-roll, up to (Attribute) dice. The parallel to these results happens at 14 dice (pool of 9 after converting). Assuming a maxed Attribute of 5 for 5 automatic successes, like the previous example a 5-or-below being automatically-successful (in this case Literally):
98% Chance to hit DV 6
94% Chance to hit DV 7
83% Chance to hit DV 8
67% Chance to hit DV 9
47% Chance to hit DV 10
29% Chance to hit DV 11
And you get a fairly-close approximation of the low-end without having to inflate the base-math very much, do funny things with the die-results, or even expand Lunars beyond their listed 5-cap trait ratings. The Success-Converting versions trail off more quickly due to the success-curve on low numbers of dice, and but given how Ex3 is so fond of adding miscellaneous dice-trick riders and such to various effects, that's not an impossible thing to overcome and level out in particular areas of focus if you're diligent enough to push for a completely different form of gameplay than what Solars are advancing. And this is just me noodling a 5 minute thought experiment, there's probably even more simpler ways to do this, but working from precedence is never a bad example.
But the matter of the fact is, they don't Want to do this kind of shit. Making everything Big Dice is easier for them to write, takes less time, and doesn't require them actually hash out the kinds of mechanics they are putting in the book. They can just assume it will work the same as anyother Charm, and plunk it in a tree somewhere behind a number of prereqs they aren't counting. And that's the real problem here, the unclear degree by which Lunars will be forced to deep-dive into a Charm tree to remotely get comparable (not even necessarily identical) options as Solars gain.
Which brings me to the problem of the Protean keyword, which is actually more of a Restriction painted as a bonus. You not only have to be in animal form, but you have to have a given set of traits for the full power of the Charm to be available, otherwise you're always using a strictly-worse version of it. There is Zero incentive to buy into a Protean Charm unless you can maximize your usage of it immediately, but even when you can, you're working from animal form limitations (no weapons/tools, incapable of human speech, for starters) and the purpose of that bonus isn't Enhancing what you got, since most animals aren't an upgrade to begin with, but serving entirely to bring you back up to parity of what options you started at.
So like most attempt to mechanicize shapeshifting, what its primarily doing isn't giving you a toolset to work from, but meant to hedge you into One Specific Hulk-out Form which exclusively benefits from every Charm you can suddenly use far more capably than before. They tested out something similar in the Alchemicals 2e book, using a restriction that demanded installing certain Mutations to increase the effectiveness of other Charms that way, and it failed just as hard by overcosting the buy-in (a Charm-slot) compared to what you would be getting out of it (a mote-cost reduction from 10m to 5m). Buying Protean effects for more shapes beyond the best dilutes your options rather than broadens them, because now you're just being several animals only Slightly better than normal, rather than one Really Buff form. This isn't helped by the fact the only Protean Charms we have seen are all activated effects, meaning you're not even getting these benefits immediately on shifting forms. You have to be in the right form, then use the Charm, and hopefully this makes you a peer-level opponent to someone else not juggling this baggage who is also using the Best version of their Charms all the time rather than selectively.
Its a critical drawback, and most Charms which push shapeshifting tend to lock effects behind it this way, and hyperfocus them into particular forms, as a method of punishing most attempts to generally use normal abilities like mobility-boosts, damage-adders and similar stuff together which is otherwise totally available to everyone else who Doesn't have to deal with shapeshifting. What if you want to look like another person, the most basic of all disguise powers? You can't use something utility-use like Perfect Mirror, you have to shapeshift because Shapeshifting is the Lunar Deal. Which means you either have to brutally murder them in a conspicuous Sacred Hunt way, or you need a narrow third-option Charm like the one in the preview which forces your character concept into a lascivious lech instead.
Solars and Lunars will never be Peers so long as they're fighting Solars in the methods Solars succeed best at, and when Shapeshifting is used as a noose to choke concepts down into using half their abilities well and the other half badly.