Bingowings said:

Simm suffered the same way Ainley did.

Both wanted to play the character in a more nuanced way but were ordered to dumb it down by the showrunner of the day.

I loved Derek Jacobi's Master though (both of them).

I'd like to see Simm return after the drums have been silenced (as source of his villainous actions temporal tinnitus is very dumb).

Yes, Derek Jacobi was awesome. The only reason I did not include him was the short amount of time he was on screen as the actual full blown character.