The reason why Ainge said he went with half and half for a second year is because he almost had a star trade in place. While I hated Ainge's smugness about another trade he didn't make, I'd agree that if you're wanting to trade for a star, you need to have the infrastructure around him to compete. We torched a lot of that infrastructure to tank. Even if we had the package for Giannis, I don't think we'd be a Giannis team.
With Giannis in particular, I think you need to be ready to compete immediately. Taking 1-2 years of his remaining prime to build the team is losing so much value.