I've really tried to put my finger on what it is about the kills in the TERRIFIER movies that I find so unpleasant, while also still considering myself somebody who loves a great gore gag/kill*, and what I've arrived at is that Art the Clown's enjoyment of what he's doing is what I find off-putting. It gives the protracted kills a kind of fetishistic quality that I find uncomfortable.
Now, horror doesn't have to be comfortable! But I think the intent of the TERRIFIER movies is that we're meant to enjoy the gore as much as Art does... and I don't, so the movies don't work on their own terms for me. That's the disconnect.
*This year's IN A VIOLENT NATURE contains several pretty extreme (and inventive!) kills that work in the context of the movie's intentions.