I agree with you that if Rey is a Mary Sue, then Luke definitely is as well. But I’ve developed a huge distaste for the “Mary Sue” label due to how thoroughly abused it’s been, and would rather just push back against it being used at all.

The original concept referred to fan fiction self-inserts, and in my opinion it really only holds any water at all in the context of a new character being forced into an existing dynamic. If it’s the franchise’s main protagonist, it’s not a Mary Sue.

After all, if Luke’s a Mary Sue, why not Kirk? He’s the youngest captain ever in Starfleet, and has been given command of their most prestigious class of vessel. He’s unerringly appealing to women, to the point where gynoids will malfunction from his charms. He’s able to best his hyper-intelligent Vulcan science officer at chess. He can bluff his way around encounters with races far beyond Federation levels of development. He defeated a eugenic superhuman with ten times his strength in direct combat.

It’s fine, even normal, for a protagonist to be exceptional. It’s a meaningless criticism to me.