Ainge and his guys are master cap manipulators, which is why the enormous jumps in the cap coming down the pike are actually really bad news for the Celts. Wipes out one of the major advantages they had over a lot of other teams with less creative management and more cluttered cap sheets.
Having cap space and maintaining flexibility is a lot less useful when basically every team in the league will have oodles of cap space.
I don't know that you're wrong, but I think you are. The massive projected increase in cap space will coincide with a massive increase in max annual salary. 60M in cap space will not provide teams with the capacity to sign 3 max players as it would now, but will only allow 2 max contracts. Deals like AB, JC, and rookie deals will be of tremendous value if the players are decent. LOTS of trade value with good contracts and draft picks.
4 ways to improve a team:
1) Player development of current roster players
2) Trades
3) Free Agents
4) Draft
You need luck and skill with every type of improvement. Skill puts you in position to possibly improve and luck puts you over the top. The C's are in position to possibly improve in any/all of the 4 ways to improve. Not much more you can ask from management at this stage of a rebuild. What Ainge does with the flexibility he's created will be fun to watch over the next 12 months or so.