Altafini insists Conceicao's approach doesn't suit the Rossonero and wants to see an Italian in the Milan dugout.
He told Tuttosport: "I respect the important goals achieved by Conceiçao in Portugal, but at Milan - after starting well with the victory of the Italian Super Cup - the results achieved have been negative.
"Coaching Milan is a different thing compared to Porto. I don't understand why the club always goes for foreign coaches, when there are so many good ones among the Italian ones.
"Among the youngsters, I think (Roberto) De Zerbi and (Vincenzo) Italiano are very good. I would see them leading a big club like Milan. The important thing, however, is that the management has a clear project. We can't make any more mistakes after this season."
Asked how Milan can "become great again", Altafini also declared: "Football is simple: you need a goalkeeper who equalises, a striker who scores, a strong defender and a midfielder who knows how to create play, then for the rest all you need is for the other players to run.
"The current Milan is missing (Simon) Kjaer's heir above all: they need to get a high-level centre-back who can command the defence and be tough in marking the opponents. In the summer the priority must be to buy a great defender."