I have yet to understand a problem with the new stat blocks.
According to Crawford, most people that play D&D want to do so for 2-3 hour sessions once a week or once every two weeks. Every change they are doing isto make it so people who play the game for this duration have ample enough resources to enjoy themselves. Streamlined monster stat blocks are part of that.
If I have a 40 hour a week job and am also running a game, I don't want to have to parse an entire freaking 1st to 9th level spell list and then have to manage 1-3 of those spell lists in a session in a fight. If I have a salary position and I work anywhere from 40-80+ hours a week, I def don't have time to go through the 15 1st-5th level spells the ARchmage has but will never use, and think about what upcasting those spells would be.
I don't have the time. I'm not the only one. It is 2022, and in America, you work more then you live. On top of that, D&D is competing with board games, video games, movies, television, books, comics, and foreign entertainment markets like anime and manga. This isn't even getting into music, martial arts, or any other hobby you could have. So to convince me, and to convince other people, to play D&D every week, which takes hours of prep across a campaign and learning the rules and so on, you need the game to play a bit lighter.
D&D obviously doesn't want to get too light. They are very happy with their current amount of crunch, and are even increasing it given the upcoming feat rules changes for Dragonlance etc. But spellcasters as they were before are a nightmare to run for a time-pressed GM, and you'll never run more then 1 at the same time because holy hell is controlling 3-4 spell lists at the same time an immense feat of focus and knowledge.
Lastly, I'm sorry, but some of you are acting so spoiled. It isn't hard to change a stat block. It isn't hard to buff it. It isn't hard to add more spells, or to say that when they use one of their 1/day spells that it counts as a spell slot of that level for whatever random reason you come up with. It just isn't that hard. And the fact that "Arcane Blast" isn't a spell your players can learn doesn't matter either. Its obviously some trick the wizard has, just like how dragons breathe fire and so on. The fact that player's don't get it is mitigated by the fact that players get a huge amount of options. They don't need an Arcane Blast, which is a filler for whatever cantrip you want it to be.
People on this forum have lost perspective with the rest of the fandom. You think that because its easy for you to pick up and play the game as is, that it is for everyone, but it is not. DMing D&D has never been easy, and making monsters easier to run is a big boon for the game. I much more prefer this new direction then anything in the past, because now I can run a whole rival part of spellcasters and not have to worry about 100 spell slots to keep track of (what a horrible thing!).
