Milan celebrated their first Scudetto in seven years thanks to Saturday’s goalless draw with Roma in Rome, ending five years of dominance from their city rivals Inter.
“This is a wonderful feeling," Gattuso told reporters after the game. "They [our detractors] gave us up for dead.
"It’s even better that we beat a rival like Inter to the title. When there’s this type of passion, you can’t help but do well."
With many of the club's aging stars set to leave in the summer, the 33-year-old midfielder believes that it is time to invest in new players.
"It’s a great victory for me personally, as they thought I was finished too," said Gattuso. “My own journey is almost at an end, but when a club invests in top players, it will win.
"I hope this win can open up a whole new era for Milan."