I think buffy isn’t tarnished, I’d go as far as to say xander is more relevant today with weird male subcultures on the rise. I think xander was a realistic character, he was often portrayed negatively and his actions had bad consequences for the group, the only problem is the show goes easy on him, never challenging his status as one of the good guys. That probably does just reflect the standards of the time, but could also work on a critical level, how society set the bar so low that someone as problematic as xander was acceptable, I doubt the later was the writers intention but it works on that level, to the point I don’t wish xander was any different, we can now watch, cringe and complain at his behaviour and acceptance, which has a critical function even if unintentional. It is a shame in season 6 when they addressed these issues with the trio that they weren’t more reflective on xander’s past behaviour and attitudes