Would you consider a transposer, a real musicians??....My answer is 'No', because you are mainly tricking people into believe you can do something you really aren't doing.
Although it is
better to be able to play in all keys, if a musician can only play in three keys, he or she is still a real musician, simply because, being a musician is not an (either/or) or (all or nothing) deal, but rather dynamic varying levels & degrees of playing.
Some people can't play in ANY key. That would be consider someone who is not a "real musician". But someone who can play in 8 keys or 2 keys or 12 keys,
"IS" a real musician - just on various levels.
Oh, and to take it one step further:
1) You might have someone who can play in all 12 keys, but no matter what you hear that person play, and no matter what key, they still don't seem to "move" you with their playing.
2) However, you might find somebody who can play in four keys, but nearly
EVERYTIME you hear that person play, they always seem to "move" you.
Now what?
.....do you say that player #2 is NOT a real musician simply because he/she can play all that wonderful, "moving" music in only
four keys?
Well...maybe he can
only play in four keys, but nearly everytime he plays, he
"successfully communicates" through the instrument. And because of that, i would indeed call him a "real" musician, (perhaps with limits), but nonetheless "real".
Finally, transposing is not "deception", but rather "limitations". He's not transposing to
"pull one over on the people", but rather because
that's the only current skill option he has.
I mean, exactly how much does the listener really care if you successfully played the song, but each time you touched a Gb, it sounded like an Ab? I'm not so sure that they're gonna hold their hands over their mouths; gasp and say: "how DARE he!"
Bottom line:
- It's important and a virtue to learn to play in as many keys as you possibly can (preferably "all 12")
- But, if you can't currently play in every key, you're still a musican, just with "key Limitations, when you do key Imitations".