Bruh, I think you're thinking too deep into this. Some people don't like the flavor profile of pineapple. It likely started as a teasing joke to their friends when they were young and didn't know comedy:

"Eeeewwww pineapple on pizza?! Gross! 😂"

And then the joke just kinda blew up from there because enough people agreed on it.

Then you become an adult and realize people just genuinely like different things. I hate pineapple in general, so I don't get it on my pizza. My husband loves Hawaiian pizza.

I love anchovies, and he can't stand them. He says the "juice" affects the rest of the pizza even when I only get it on my half.

We order 2 different pizzas and everyone is happy.

I don't think either of us (or anyone who still pretends to be shocked that pineapple on pizza is a thing) is "gatekeeping pizza" or shaming poor people from tryna eat whatever they have. It is legit on the same level as. "OMG you use APPLE?!?!? I COULD NEVER!".

It's just harmless teasing.