Alonso praised his new Aston Martin team-mate, telling the team's official website that Stroll has the potential to be one of the best.
"In Lance, the team has a driver who is super young, super talented and has the possibility to be World Champion. To see him achieve that and have played a part in that, whether that's behind the wheel or not, will be special for me."
It is not the first time Schumacher has criticised Stroll, with his most notable dismissal coming in March 2022 when stand-in driver Nico Hulkenberg outqualified Stroll for the Bahrain Grand Prix.
“Stroll should ask himself about whether he should find a different hobby, it was really embarrassing.," he said on German broadcaster Sport1.
"It's an understatement to say that he was beaten by a team-mate.
"I believe that when someone who has not driven for a year and a half comes in and is three tenths faster than you straight away, you should think very carefully about whether you are doing everything right."
Schumacher spent a decade racing in Formula 1, winning six times and finishing on the podium 27 times. Stroll has yet to win a race and has just three podiums in six seasons.