What qualifications do you want him to have that he doesn't? He's smart, affable, likeable, charismatic, and can relate to voters well, seemingly. He also has the connections to raise the money necessary to win from the many different personal and professional networks he has as an actor, activist, union member, and friend of Obama's. As well, he served on President Obama's cancer research panel.
He's lived in Detroit since 2016, so no, he's not a lifelong Michigander. But I think he's got as good a shot as Slotkin at beating the presumptive Republican nominee. The best candidate the Republicans have been able to recruit as of now is State Board of Education member Nikki Snyder and no one else even remotely serious. Congressman Bill Huizenga and former Detroit Police Chief Hollywood James Craig have expressed some interest in running, but have not declared. If they don't, barring some repeat of 2016, it should be a solid year for our Senate Democratic nominee. They don't have a John James type candidate to run this year that we need to be as worried about.
For me, it's about picking a quality candidate who can win and has been on the right side of history. Slotkin was a CIA Analyst in Iraq. She would be yet another candidate who was a supporter of the Bush Administration's unlawful and immoral War in Iraq. I think you can look at that as a judgement-based critique of Slotkin.