Ten hag wasn't in a tough league, and secondly he was in the toughest club ruling a weak league for that he had better advantages. I will support it if u said Ten Hag is more experienced than Xavi but saying that he is a better coach than Xavi I will say u judge based on the current performance. Becaquse the same reason should make u rate him above Artetta but because Arteta is doing well, u wouldn't say Ten hag is better than him.
Basically I have never blamed any coach for the team they lead, either in the past or at the moment. Regarding experience, of course everyone has seen how Erik ten Hag coached other teams before Manchester United, and everyone also knows how Xavi was when he first coached Barcelona because he is a young coach among most other coaches so there is a clear difference in experience. Talking about the good and bad of the team they coach, it actually has to be assessed thoroughly by not cornering just one person like the coach.