First off, we should never forget that football is a contact sport, meaning that (unlike for example volleyball) to touch an opponent doesn't equate fouling.
The contact between scamacca and the Ukrainian player was overall soft.
More importantly, scamacca simply did his thing, he was in possession of the ball and his movement was natural and coherent with was he was doing. If anything, a foul should have been in favor of Italy.
Fucking ref, I hope he's not allowed to umpire an important match for at least the next 5 years.