My thoughts: a great QB will become great no matter what (barring injury). Things might look ugly as they learn, but they're not going to lose their confidence. The great ones aren't fragile mentally. They can accept adversity.
There are other QBs, who can be successful, but only under near perfect conditions. If Maye is one of those guys, then yes, you could do some long-term damage by playing him as a rookie. But, if he's truly a franchise player? I think he would survive, the season, and would thrive going forward.
My biggest worry about playing a young quarterback would be the risk of a career altering injury. I think the mental stuff is overblown. Mac Jones is used as an example, but Jones was never going to be a top-tier QB.