>both over-abstracted and inflexible which made it really hard

This seems to be built into the culture of companies which have those ridiculous whiteboard leetcode interviews. You find people who can produce very clever complex solutions in their sleeep, and then they do that. Interviews aren't selecting for people whose strength is simplicity and clarity instead. So you get a lot of tight loop optimizers and they tight loop optimize everything... not just the tight loops. But if your product is a library/framework being consumed by mere mortals, you probably want something simple if you want to succeed in the long run. The super car's performance is meaningless to you if you can't drive stick.

Yeah, clever code is the bane of my existence.

Only my own code is allowed to be clever!