Microsoft doesn't need to care about backwards compatibility anymore, now that Wine exists precisely to have compatibility with Windows software (including software that even modern Windows itself no longer wants to run).
Wine is 26 years old.
Depends on what you mean by "good enough". Wine is an incredible project that has achieved amazing successes, but it still falls short in a lot of ways.
I personally don't use Wine but I've encountered people online in the last 10+ years that use the argument that it's "good enough" for people to fully switch to Linux. Realistically, I don't think Wine actually convinced more than a handful of users to abandon Windows