I agree that it is different for SOME singles (not all) than it is for struggling married couples. I think you are WAY more differentiated than you were when you first showed up here, and I'm pretty certain that has had an impact on what improvements you've been seeing in your marriage.
I've come to see/learn lots of things about myself that I have no doubt would have helped my marriage. Lots of good that will do my ex, huh? And no, I still don't regret my decision.
The further you differentiate, the more change you will see. I'm telling you that from hindsight, not from the idealistic world you seem to think I now live in as a single.