Maybe it was too early for me, but I was reading it as having more generic subclasses, that would then increase complexity by increasing decision points.
Hmm no, subclasses would stay the same as now, but it would open the door for stuff they tried and failed in the past, like the college-based subclasses in Strixhaven that could be used by any class.
For example, I have a published setting, Scavenger. In Scavenger, I narratively divide classes into four groups vaguely the same as what 2024 was trying to do in the UA's. If we still had standardized subclass leveling (3, 6, 10, 14), I could make subclasses for those groups that provides a more seamless connection between narrative (the four groups) and mechanics (12 individual classes).
This isn't unique to my setting, as I already talked about how Strixhaven could do it. But Eberron could have as well, turning Dragonmarks into subclasses instead of Backgrounds. Dragonlance could have had Red, White, and Black Robe subclasses instead of backgrounds, which IMO would have worked better too.
It doesn't work for every setting, but since the only thing truly necessary in this situation are standardized class levels, it doesn't have to work for every setting. You can still have flavorful class-specific subclasses such as the Bladesinger or World-Tree Barbarian. In other words, this small change sacrifices easier backwards compatibility but opens up the door to far more interesting concepts that IMO would really make the game sing.
You could even go further. Instead of relying on the Renown System for Theros and Ravnica, you could have God or Guild subclasses etc.
Now, I realize I'm partially biased here. As a designer, of course I want a game that lets me play with it in more interesting ways. But I also think this would benefit casual DMs/players because it keeps character creation in these settings streamlined. To play Theros, I don't need to learn about this Renown system and gaining Renown points and tracking benefits that way; instead, I have my subclass "Demigod of Heliod." These class-agnostic subclasses could easily be designed to offer benefits that apply to most classes, if not all, so it also wouldn't be a big deal making subclasses that fit every class.
These are just my thoughts. I know that many people are comfortable with the system as is and I believe that comfortability is valid. I like 2024, and I like designing for it. But I feel like sometimes comfortability gets in the way of GOOD progress. Not progress for progress's sake, not change for change's sake, but actual GOOD innovations that could improve everyone's game.