I absolutely use semicolons when writing professionally. They're just basic parts of grammar, and if you want to be taken seriously by some parts of the world (academia, I'm glaring angrily at you), you would use them.

I guess it comes down to expectations? You don't expect formal conventions from a website writer, while I absolutely do.

I find it interesting that it was a flag for AI writing for you. That's going to make me consider my voice in certain situations now.