Most phones can't be rooted because the bootloader is locked. Somewhere there's probably a list of phones that can be rooted. I found that Google Pixel phones that were sold directly from Google can be rooted, you can know them because they mostly come in different colors then what a Google Pixel, say from Verzion comes in. But I'm not really knowledgeable about this, I just did it once.

There is a at least one list that I saw a few years ago. But even then they warn you that there's always a chance you'll brick your phone.