this has nothing to do with under- or overpowered, only with how easy it is to use 2014 subclasses in 2024. So far that looks pretty straightforward, and I have no reason to believe that it will become less so
What it has to do with under- or -overpowered-ness is that WotC is not necessarily all that good at tuning things well or including everything they need to include (see: Spelljammer's ship combat rules, or lack thereof). I see no reason to think that they're going to be magically better with this supposedly-backwards-compatible not-edition they're putting out.
I am not saying there will be no issues whatsoever, but your concern seems way overblown.
Have you
ever read any post by any D&D player who gets into the rules nuances? Like,
ever? Heck, look at all the vitriol that's been spilled on this forum by WotC officially getting rid of racial ASIs in MPMM. Some people absolutely
hate it, causing multiple threads, each many hundreds of pages, to be created and later closed by the mods due to the vitriol. And that's just one little thing that doesn't even prevent the player from putting their floating ASIs in the traditional attributes! And you think a book
full of these little changes, that can't be unchanged without switching books,
isn't going to cause problems?
I mean, '14 could turn out to be great. No major issues whatsoever. Which brings me back to my initial post to this thread: by making it not-5.5e/6e/5e Essentials, they're making it so I, and people like me, have no reason to buy it whatsoever (it's not different enough to be worth the money). And while that's fine--it doesn't have to be marketed to me, it's great that it's there for new players--what it means is that if I, or someone like me, gets into a game with someone who
did buy the new books, things are going to be confusing. And not in a way that's going to be fun. If it were
my table, we'd gladly give each other the necessary rules, or show each other the books if we were gaming in-person. But there are a lot of tables where that's not the case. And, as I've mentioned, a lot of people who join groups with people they don't know and are expected to come into the game with a fully-fledged character.
One game I'm in has two warlocks in it. Imagine if one is from '14 and one is from '24. One of those warlocks would be probably quite underpowered and feeling left out. And I imagine that other classes have similar issues. A '24 ranger is going to be better with ranger knowledge than a '14 ranger will be.
Which means that the best way to do it might very well be to only allow one set of PHBs at the table--which means that some people will have wasted money, which means that these '24 books
might as well be a new edition. Except they're
not, because they're not different enough to be called that.
So far you have nothing but a vague feeling, you will need more to convince me, so I suggest we revisit that once the 2024 books are out. Until then you have nothing, as you yourself said.
Well, so far all
you have is a vague feeling that everything is going to turn out all right. So I don't know why my vague feeling--backed by the way WotC's books have historically been written--is one to be dismissed.