That is the view of Schumacher's former race engineer, and ex Ferrari academy chief Luca Baldisserri.
Vettel has fallen short to Lewis Hamilton in title battles the past two years, and is not even a factor in the 2019 race, sitting 100 points behind the Mercedes man at this season's halfway point.
Poor strategy, a struggle to optimise the SF90 and continued mistakes from Vettel have made for a potent mix this year, prompting question marks to be raised over the German's future in the team and F1 as a whole.
Despite explaining his frustrations with modern F1 after having a victory in Canada taken from him by the stewards, prompting rumours of a potential retirement, Vettel says he will at least see out his Ferrari deal which runs to the end of next year.
However, Baldisserri says that Vettel should do so with the "priority" that team boss Mattia Binotto has bestowed on him this year given to team-mate Leclerc instead.
"I am critical of Vettel. I think he is overrated driver, and not the successor to Michael Schumacher," Baldisserri said on the Pit Talk Radio podcast.
"This is still the driver that won four world championships, but he makes too many mistakes and has to find himself in some way.
"When Leclerc becomes a more mature and experienced rider, he will need a team mate who can help and support.
"I believe that Vettel has the necessary experience to become an excellent partner for Leclerc."
Vettel still leads Leclerc in the drivers' standings, albeit by just one place and three points after a British grand Prix which saw the German throw away a potential podium finish by crashing into Max Verstappen.
GPFans is a multi-platform, multi-language brand dedicated to Formula One coverage. We bring you all the ins and outs of the sport, 24/7, everything from up-to-the-minute news and features to the latest viral stories and clips.
We believe that a new generation of exciting, outspoken drivers will make F1 more popular than ever before, and we want to give our users access to as much of their heroes as possible, on and off the track. From Lewis Hamilton to Max Verstappen, Daniel Ricciardo to Sebastian Vettel, we provide in-depth analysis of every every Grand Prix in the season, from Australia to Abu Dhabi.
With Formula One under the new ownership of Liberty Media, how the sport is being covered is evolving, and GPFans will look to be at the heart of this progression into new media, as one of the fastest-growing sites covering the king of motorsports.