The problem is that you can't make these judgements in a vacuum. The current situation the Celtics are in is they need to compete now while Thomas and Horford are in their peaks. They are trying to do that without just recklessly throwing away their valuable first rounders, unless a star becomes available. Thus, they can compete while also nursing the next generation in role player, not main roles.
I think that they considered George as a good enough player to deal and eventually pay a max for, but Indiana seemed to have their own agenda that wasn't necessarily based on getting the best possible deal. Also, George is most likely still going to run to the Lakers in a year. Was it a risk waiting for Hayward? Yes, but they were ultimately rewarded. Also, I think you're underrating Hayward a little here. He's not LeBron or Durant but then again, who is? Hayward potentially could play himself into the 2nd tier somewhere.
The way I judge a contract is by asking myself if the player needed to be moved tomorrow, could you get rid of the contract easily without giving up any assets? The answer to that is unequivocally YES, as Hayward will be making a lot but he will also be in his prime and he's not injury-prone.
You're right that in terms of production per dollar, Crowder is going to give more than Hayward, and everyone knows players with talent on rookie deals are the best bargains in the league other than super-superstars. The problem is that super-superstar is not available.
Let's say there was a team full of guys like Crowder on super cheap deals. How far would that team get in the playoffs? Not very far, even though you'd be getting amazing production relative to how much you're paying. You'd also have lots of empty cap space with no one "worthy" enough to spend it on according to your strategy of maximizing "value."