I think there are a lot of valid points in the op, to be fair. I'd have agreed with it until maybe February. The season was shocking and there were almost no positives apart from the fact that we'd gotten rid of a few players I hated.
Still, the last 15 or so games have mostly been excellent, we showed title challenging form in them, we were a joy to watch (until the last few) and our young players were showing cracking improvements as well as players previously on the cusp like Matic and Pogba.
So while I think overall it has been a bit of a rubbish season, the last few months were so much better than just about anything we've seen in years that I think it's good to be optimistic especially as we were lucky to get in the CL despite our low points total.
Put it this way, I'm a lot more confident going into next season than I was under any LvG or Moyes season, and Mourinho's 3rd season. I don't think we'll challenge but I expect us to be a 70 to 80 point team again which is OK for now. Ole is doing a pretty good job and building a good side for our next, better manager.