It’s like you only read one phrase out of context.

It’s a completely ridiculous position.

That some food is better with minimal seasoning?
That the amount of seasoning you put on a food is somehow related to the nature of the ingredients?

I season my food, which is delicious btw

I’m glad! I never said you shouldn’t. I said some ingredients don’t need it as much, or are better enjoyed with minimal seasoning.

and so does the rest of the world outside of northern Europe.

I’ll remember that the next time I eat sushi.

The classism came from the aristocracy making a display of wealth by choosing to ostentatiously eat the foods that benefit from less seasoning, and casting the others as “low class”.
That doesn’t make the method of preparation a relic of classism. It’s classist to say that a pot roast is low class, not to say a ribeye doesn’t need much to be delicious.

Modern British food has a reputation as being unseasoned because we don’t call any of the seasoned dishes born of their empire “British”, and a lot of the other stuff got messed up by “island nation in a major war with prolonged food rationing”.

Remember that the flip side of the aristocracy avoiding seasoning to distinguish themselves is that everyone else didn’t.