As you point out, pianist can't deal with it via pitch alterations; but
we can do things with timing, dynamics (including chord 'voicing'),
possibly articulation. Those are the three things we have to work with.

True... and the whole time, you are playing an instrument that is
conveniently "autotuned" for you. Wouldn't your definition of the word
"musician" require that you play an instrument over which you have full
pitch control? Wouldn't using a piano, a keyboard, or autotune constitute
cheating?

Bottom line... to assume that any vocalist who's ever had an ounce of
Autotune applied to his/her voice is not a musician is quite the extreme
generalization... and I'd say just a bit unfair.

The world of music has really gone downhill when artists start determining
which other artists are "real musicians" and which are not by some
preconceived specific definition of the word.

-S