Personally I feel a great deal of sunk cost as a late-in-life diagnosis. I kind of sympathize with both sides because I had to learn to mask without even knowing I was masking or that it was a thing I was doing. Now when I think about just 'being me' it feels impossible and like starting over trying to deal with people I've never understood to begin with.

It's tough. I wouldn't be too hard on either. For some people masking just keeps things from spiraling out of control, and for others it's an effort that causes strain the other way around.