There are a few things you can do to humanize your MIDI:
Shift the midi slightly off grid – Humans do not play perfectly on the grid, moving notes backward and forward a few ms in different amounts will make the piano sound like its being played by a human.
Change the velocities of different notes – Some velocities should be soft and some hard. This will inject energy and emotion into the piano and make it sound more real.
Add some light reverb – This will put the piano in a space and make it sound less dry and robotic.