I think the problem is that there's a fine line between criticizing and bashing. Xander as a character has aged poorly, mostly because of changes in social attitudes in the past 25 years. But even accounting for that I wouldn't describe him as the worst character ever, and yet you're right that he gets described that way. There's even a YouTube video with roughly that title.

I haven't re-watched in quite a while and I really should. I've been trying to catch up on shows I've missed, but I'm starting to run short. I do enjoy your comments as you re-watch; that length of time between viewings can really change one's perspective.