I thought getting regularly infected with seasonal diseases keeps your immune system up-to-date against the pathogen mutations and avoids a rarer but more dangerous episode down the road.

But I guess without a serious study my belief is hard to check & validate.

It's the opposite - regularly getting infected weakens your immune system. It's not something that constantly needs to be "trained".

What we normalize is not stopping the world every time someone gets the sniffles.

What we have normalized is forcing people to work while sick, so they can make everyone else in the office sick.

So you're the one passing the cold around. Please stop doing that! We all resent it.