Perhaps there could be a way to balance it out by giving a carapace armor set some sort of alternative ability that makes it useful in the end and/or as a late game armor set similar to elytra, but filling a different niche.
To be fair, I do think there's a good reason we can't wear elytra with chestplates- it's a trade off, but to be clear Reaver said pretty bluntly that it should be difficult to equip elytra and a chestplate at the same time. ...I don't really think you should be able to wear armor with elytra- however, that doesn't mean that any new material or armor set would be completely useless. There are numerous other ways a new armor set could be utilized to serve some sort of new aspect of gameplay. ...That being said, I'm not entirely sure what that new aspect might be- it really depends on how hard carapace is to get once you're actually in the end, though, considering that it is the end, it's already going to be pretty rare.
-One idea is that carapace could be an additional upgrade to Netherite- offering some sort of special boon, like making it easier to enchant.
-Carapace armor could provide the player with a sort of hover feature that would act as significantly more controlled flight than elytra, but would not be at all as helpful for covering long distances. This could be themed after the insects themselves.
-Perhaps carapace has some other weird/helpful special abilities that help players navigate in the end- such as a helmet that prevents endermen from attacking, but doesn't obscure your view like a pumpkin.
Again, these are far less full fledged ideas than me trying to make a point that there's more than one way to implement more content- an entire idea shouldn't hit the shredder just because one aspect of it seems a bit unbalanced.