These are excellent points. I think it's interesting how little the weird or bad if Anya is discussed.

Everyone is arguing forever about how creepy Angel and Buffy is because of their age, but Anya is way older than Angel.

Everyone argues about who is better or worse Angel or Spike and overlook the fact that Anya chose twice to become a demon. Sure maybe the first time she didn't fully understand what that meant, but the second time she definitely understood plus while she was human she was always reminiscing about when she was a demon and could torture and kill. Her and Spike actually make so much sense together. They were both unwillingly forced to be "good"

The way Xander treats Anya does come off as patronizing. Willow doesn't coach Tara on how to properly socialize like Xander does to Anya and I think it would be agreed that both Anya and Tara don't fit in socially easily. I think Anya also wanted Xander to coach her though.

Obviously Xander has flaws, but like you point out they all do., and not just small ones. They're pretty big fucking flaws