Now with Alisson gone Donnarumma is probably the best available option left, and for a reasonable price (approx €40/45m).
The problem might be he has a huge salary plus a useless brother who will come with him.
From a football point of view he can make unbelievable saves and awful mistakes in the same game. Actually there have been too many mistakes only in his last season, more than Tibo has in his whole short career.
Two season ago no one would have chosen Alisson over him, the first one was a bench warmer in Roma while Donnarumma the highest-rated young goalkeeper in the Europe (he could still be up there).
Last few things: worse than Tibo with his feet, a real calamity, Sarri called him a sensational goalkeeper when Napoli played AC Milan this season (Donnarumma made a couple of incredible saves that day).