you aren't really good on an instrument until you can play in any key in my opinion

A good criterion, but there are instruments for which that is an impossibility. The twenty button anglo and the diatonic harmonica are both examples.

Perhaps then the measure of a really good player is someone who can go beyond the apparent limitations of an instrument.

I also suspect that all instruments are equally hard to play at some level. Some make it relatively easy to get started, but then the difficulty level ramps up when you go beyond the beginner stage. Others are hard to get started on but then plateau so you can make fairly rapid progress after you are over the initial stages.

To play at top level on any instrument takes total dedication and hundreds even thousands of hours of work. Much as I enjoy playing my instruments I am never going to be better than competent, but as long as I enjoy my playing, can hold my own in a session and occasionally give others some pleasure, then I am happy. It is also important to continually strive to improve.