Speaking exclusively to Football Presse, Incocciati suggested Leão has struggled to cope with the pressure that has come with increasing criticism and does not believe the Portugal international will remain at Milan.
"I believe Leão's future is no longer at Milan," Incocciati said. "Leão's qualities are not in question. The only thing is that, unfortunately, he has not learned to manage his emotions, his behaviour and everything that comes with being a player at that level.
"He has ended up in the sights of criticism and, honestly, he is showing that he doesn't have the reactive strength to answer those criticisms."
Incocciati's comments come amid continued uncertainty surrounding Leão's future, with speculation over a summer departure continuing after another disappointing campaign for Milan.
However, the former striker believes focusing solely on Leão misses the bigger picture, arguing Milan's problems extend far beyond one player.
"When clubs become multinational companies and only look at profits, then when the results don't come, people pay the price," he said. "I'm talking about the coach and those responsible for the football side of things.
"Unfortunately, these have been Milan's difficulties over the last few years."
Incocciati believes the club lacks an essential link between the boardroom and the dressing room, leaving the squad without the support required to succeed.
"Milan do not have a structure that connects the needs of the club with what happens on the pitch," he explained. "The team has been left a little to itself.
"In my opinion, results come with the support of everyone.
"From the ownership to the last massage therapist, everyone has to give the best of themselves for the team so that the players can go onto the pitch with peace of mind.
"That hasn't happened in recent years, and the results reflect that."
Incocciati also questioned the growing influence of investment funds in modern football, suggesting financial priorities are increasingly dictating sporting decisions.
"The funds that own clubs look at profits," he said. "That's the reality of modern football."
He pointed to the departures of key players from Atalanta as another example.
"If players like Ederson leave, it's because the club believes making a profit is the right decision. That is the only reason they leave.
"But Atalanta have shown over the years that they already have other players ready to emerge."
While critical of AC Milan's recent direction, Incocciati praised Inter Milan's stability and believes the Nerazzurri remain the benchmark heading into the new Serie A season.
"I don't know if Inter will win another title," he said. "But they remain the best-equipped team.
"Giuseppe Marotta and his staff will certainly make another important signing.
"For me, Inter are still the favourites at the start of the season."
Despite his criticism, Incocciati believes Milan can return to competing for major honours, but only if the club rebuilds from the top down.
"The whole environment has to work together," he added. "Only then can the players express themselves freely on the pitch.
"Without that unity, it's very difficult to achieve consistent success."