The Celtics haven't been a contender in 4 seasons and haven't ever bottomed out. That is the middle.
They had a bottom 5 record two seasons ago.
Maybe Ainge could have waived or trade-dumped some veteran guys (e.g. Humphries and Bass), but for the most part that was as close as you can get to the bottom without indulging in outright sabotage and trading guys off for pennies on the dollar, a la Philadelphia.
TP!
I'd also argue that part of the bottom out was the trade with the Nets. So we really haven't seen the complete benefit of the year they bottomed out.
As to Ryan Anderson for Kelly, I don't understand the reasoning. I'd much rather have Kelly, who is comparable to Anderson under a rookie scale contract than Anderson at the 10-15 MM he probably is going to get next year.
Trading long term assets for short term ones is a terrible idea.
Now we're getting somewhere... and half a season short-term at that. 
I disagreed with you on another thread about dealing Sullinger instead of Olynyk for Anderson.
To me, the difference is that I don't see Sullinger as a long term asset. I see him as a guy who we don't move at the deadline, signs a larger contract than he's worth, then immediately gets injured and becomes a liability.
You don't have to sign him if you don't want to. That's a different discussion all together in my view. And I have no problem in trading Sullinger.
But for Anderson? For half a season? A move which would actually make us worse (unless that's part of the interest, being worse and improve our draft position) considering our team... then yeah I can't get behind that.
But I'll leave it at that since this is a KO-Anderson thread.