Mary Sue characters are really boring to watch. They can do know wrong, are perfectly skilled in everything necessary, and have at most superficial flaws. Rey can somehow grow and harness her force powers in hours, something that took Luke two movies to do. She can out nerd Han Solo on his own ship, despite being a complete novice in piloting a ship and being a scavenger, not a mechanic. It’s not believable, it’s immersion breaking, and it’s ultimately lame and boring.
Those characters you named aren’t Mary Sues because they actually have flaws. Batman is haunted by dark memories, Spider-man makes grave mistakes, etc. What the hell do Bella and Rey do wrong that punishes them?
The reason we don’t have strong non-Mary Sue characters is because of people like you — the sheep who bleets whenever we ask for anything short of perfection in female characters. You demand we lower the bar for female characters (“Mary Sues are ok!”). You do not understand the subject matter (Luke Skywalker is gifted but he’s far from a Mary Sue). You think “fragile masculinity” is an actual argument.
Try harder. I won’t lower the bar for you.