The rumor mill drove expectations sky-high, even among the media. That's why there was disappointment when George went to OKC. As fans, we obviously wanted a super-duper team. Media members wanted the best story, and a team that might actually legitimately contend with the Warriors would have been more interesting than Westbrook and George teaming up for a year (come on, we all know he's going to leave).
It was these increased expectations (and admittedly, the trade of the #1 pick) that made a successful offseason look like a slight letdown. However, unless you can tell me exactly what happened with Pritchard and the so-called phantom offers, or whether the Celtics owners were really willing to pay four max contracts (it could have easily been an Indiana leak to try and get better offers from teams like LA for George), or get into Paul George's head and know what his true plans really are, it's extremely unfair to criticize Ainge for not going as much as he could have. We don't really know if these apparent best-case scenarios were ever realistic in the first place.
We signed the best free agent that was actually on the market. We gained a valuable 2018 draft pick. That seems like a good offseason to me. Anything else is speculation.