Artificer

Personally, I regard the role of the Artificer class as a home for very specialized niche concepts that require a bit of magic and strong reliance on some kind of props or gimmicks. I consider the complexity of the Artificer base class to be medium high, and think that subclasses should lean into more complexity with a narrow focus but a high skill cap.

I think that a strong central premise is a necessary anchor for an Artificer subclass to be good, and I think such subclasses should start paying off on their core premise immediately at level 3 and consistently throughout the levels. A subclass that is scattered, offering other options but waiting too long to pay off on its specific idea is just not worth its weight.

I also think that, moreso than other classes, Artificer subclasses are more setting constrained. As a DM I might be willing to allow some Artificer subclasses in given campaign but not in another because some of them require (or at least strongly suggest) a certain technology level or feel to be present in a setting and it isn't always a good fit.