That’s always been the case, right? Fitness is easier to track progress with. I fell into that trap many times.That resonates with me regarding the ftp being one part. As a person who focuses on skills and technique more than fitness i feel like some times fitness is all people worry about (not you).
One great thing about having a coach (who is an ex national champ in XCO, as confirmed by @Pearl when I had doubts lol) is that I told her I wanted to make a point of getting time on dirt. And every week there is at least one workout on the MTB on single track. (sometimes structured sometimes not).