It did get pretty zany at times, but I don't think most people were saying that after the Slade arc in season 1, or the season 2 premiere "How Long is Forever?" As
@LordYam said, the original Teen Titans cartoon knew how to get serious, and did it well. It was something that had a bad rep at the start, but grew on people when it had a chance to prove itself.
Much like
Beware the Batman which had a negative start - in part because it "replaced" YJ - but if you followed it through to the end it was a very good Batman show. Unfortunately, it too would be screwed thanks to Cartoon Network and their apparent hatred for anything more serious than a Bug Bunny cartoon; and I'm guessing those execs would've hated even something like "What's Opera, Doc?" if it came out today, because it's 'too serious' for cartoons or whatever crack they're smoking at CN HQ.
Yeah, CNs handling of their cartoons can get quite abysmal when you see that, over the course of the past 18 years, they've been focusing on more "comedy" and less "action". I think it was until '10 or '11 when I jumped ship from CN for the most part, and would normally jump to the channel to watch shows that interested me. Because of executives switching out throughout the years, we see the focus shift leaning towards one thing or another. CN Real was a thing, and that fell on it's face (and it was a painful attempt at being like Nickelodeon). Let's not also forget that CN was responsible for pulling the plug on Toonami way back, just as it was wrapping up some filler stuff for some of their shows.
It's maddening, especially when you think about how CN used to be balanced between shows and their blocks. They were able to gain the attention of different target audiences (from kids growing up, to the adults who probably remember the classics, and managed it for both genders regardless). A diverse listing of Dexter's Lab, PPG, Grim Adventures, Johnny Bravo, BTAS, Courage, Scooby, Tom & Jerry, Loony Tunes, and so forth - you get a balance.
And they bungled it. Either because the show(s) are attracting the wrong audience, or they just don't like it/get it (I'll never forgive them for writing Megas XLR as a tax cut!).
Now look at the schedule you have for CN, and some of it are reboots that no one asked for, or just don't capture the audience's attention (TTG dominate the airwaves, Ben 10 was rebooted, and shows like Steven Universe and Adventure Time tend to get the shaft). In fact, this weeks schedule is dominated by three shows (TTG, We Bare Bears, and Gumball - I looked it up). While I get that in the mornings, it's alright for shows to be comedic, the schedule doesn't change all that much from these three shows. You'll probably get a break with Unikitty!, Ok K.O.!, and Craig of the Creek, but that's not until 1 or so, and they set it up as hour blocks of these shows. And again, TTG dominate the airwaves, more so than it should.
There's no specific blocks like Toonami (when they used to air in the afternoons) or Miguzi, or even Fridays for new episodes of shows to air, to break the monotony that is CN's schedule. Hell, who remembers Saturday Morning Cartoons, because I do (and Fox Kids was my haven)? This is now an age where the foundation of cartoon scheduling and interest is different than what some of us are used to. Channels like Boomerang, Nicktoons, and Disney XD have these new shows that can garner up interest on their main channels (the companies' bread and butter), but they don't air them on it at all. Instead, it's practically the same shit over and over again, like an endless loop-de-loop.
This will not change until one of the channels breaks the mold, and I would say CN could do it, but they would need a change of executives for that to happen, which isn't likely for a good long while.
P.S.: I'm still pissed about Megas XLR.