I made a similar thread about this issue.
Posting for visibility, would prefer less rooms or a boss checkpoint mechanism.
As far as it being “the current end game”, so what? Once you get to level 30, having to spend 15 minutes repeating 8 boring rooms for a single attempt at the boss isn’t fun. There’s no “engaging challenge” in that.
The current iteration of the crucible is probably a “placeholder endgame”, and presumably could be changed to make it more fun and enjoyable while they work on the rest of the game.
If someone wants to get more hours out of the game they’ll make new realms and new characters. Being forced to spend hours clearing trash rooms to have a go at the current hardest boss isn’t fun. Fighting the boss is the fun part, the rooms are just padding.