Regarding the illusionist, I find the subclass features disappointing. These are the kind of problems I have with DnD in general. I don't like the way there are clear better choices between subclasses. In my opinion, it should be worked on across the board, system wide.
D&D5 was designed for pen and paper, not computers, though. In computers, raw combat power is suddenly more important. BG3 is actually pretty powerful in this regard; playing a Bard is so fun exactly because you get so many dialogue options.
Powergamers will always say one class is much stronger than another. Its their way of thinking. No way around it.
