I’ve seen a lot of people complain about how Gabe isn’t as bad as in the books, which valid complaint to have, but also. They had some good reasons for changing it.
You can get away with a LOT more in books than you can with visual media, because whatever you read is limited to the reader’s imagination. That’s why some notably violent kid’s books (Warrior Cats, Watership Down, etc) are still considered kid’s books. A child can still be terrified by those books, but ultimately they can only be as afraid as they are imaginative, and as long as the child is old enough to understand that fiction can’t physically hurt them, it’s fine.
But with visual media, you are only allowed that imagination if something happens offscreen. There’s a big difference between violence in words and violence visually. This is ESPECIALLY applicable to live action media, if the show came out as a cartoon then that might be a slightly different story.
Abuse isn’t fictional, they aren’t going to be as lenient with it as they might be with fantasy violence. Reading abuse isn’t as tense as actually seeing it on screen. So while Gabe’s portrayal in the book might be touching for kids with bad home lives, to have that same portrayal in the show could be potentially very triggering and scary. Remember, this is a show intended for kids.
Also, Disney can get very pissy over violence (especially violence based in reality). Most parents don’t want their kids to see realistic abuse, and if they complained enough about it, it could be a problem. Disney doesn’t like taking risks. If the show got too real, there’s a chance Disney won’t greenlight another season.
Does sanitizing Gabe’s abuse alter Percy’s and Sally’s characters, and create a mess for the Medusa plotline? Yes. Am I happy about it? No. But ultimately, I think it was one of the better options.