It is kind of bullshit, that's for sure.
On the other hand, it's probably not going to affect the game very much.
Based on the way Hoyo has done things up to now, I'm guessing that the highest level of Stygian Abyss that gives the gold weapon skins (can't be bothered to remember the name) will be scaled around you having all level 100 characters. The second highest that gives the blue weapon skins will be scaled around you having a level 95 main DPS. Along with maybe level 12 of Spiral Abyss. But it will still be doable with all level 90 if you're good. Hell, there will probably be some maniacs who clear the highest level of Stygian with all level 90 teams and post it on YouTube just to show everyone it can be done.
And, of course, 99% of the content will continue to be easy to clear with level 80, 4 star weapons, and mediocre artifacts.
man - noun. A miserable pile of secrets.
EXAMPLE: What is a man? A miserable little pile of secrets. But enough talk, HAVE AT YOU!