Screens aren't inherently bad. It's about the quality. I think your instincts are 100% spot on, keep trusting them.
But quality/distractions aside, there are other dimensions to consider. For example, reading does take more effort than most videogames, and that's brain exercise that will make a difference in aggregate (the assumption being that books and videogames are both entertainment, they compete against each other to some degree, and doing a lot of one means you'll do less of the other). So in short, playing videogames a lot isn't bad in itself, depends on the videogames. But on the other hand books have additional positive sideffects on top of the primary effect which is entertainment.
But quality/distractions aside, there are other dimensions to consider. For example, reading does take more effort than most videogames, and that's brain exercise that will make a difference in aggregate (the assumption being that books and videogames are both entertainment, they compete against each other to some degree, and doing a lot of one means you'll do less of the other). So in short, playing videogames a lot isn't bad in itself, depends on the videogames. But on the other hand books have additional positive sideffects on top of the primary effect which is entertainment.