I play a B/C button accordion so "I can in theory play in any key provided I can find the notes". The downside is that I can't do as much chord and bass stuff, but I'm finding more and more right hand chords as I go along.
I've now reached the stage that any strange key is a challenge rather than a no-go area, flat keys being more tricky, tho' not impossible. I did do a lot of music theory in my long-distant youth, so I know how many sharps or flats I'm looking for, or can tell others in the session what key the tune is actually in. Being a guitarist also helps as I can guess from chord shapes and which fret the capo goes on what key is being used too.
As for " all inclusiveness", it is good if the majority of music is accessible to the majority of players for a good proportion of the time, but if you never do anything new, sessions can get horribly predictable and boring. Playing something different is not necessarily showing off: it may well be injecting new life into a session especially if the tune can be slowed down to allow others to pick it up.