Creepypasta movies have a bad reputation for a reason. I have to respectfully disagree with your point when it's made this broadly, though.

In the mid- to late-2000s, when people first started using "creepypasta" to describe a certain kind of horror story passed around online, the label had a fairly specific meaning. Creepypastas were typically short, almost always anonymous works of fiction posted to websites like 4chan (where they predominated on the site's /x/ paranormal board, usually accompanied by unrelated but disturbing image files) that could easily be copied, pasted, and shared by any user. They were a little like Internet urban legends, although their veneer of credibility was usually thinner thanks to...well, the nature of Internet culture, and it's hard to imagine how most of them could have been fleshed out into a full-length movie.

Since at least the 2010s, though, the definition of creepypasta has broadened greatly. Some long-form stories existed before, but now they're much more widespread, and quite a few have enough content to serve as at least the nexus of a much broader mythology. Some, far from reading like digital versions of traditional urban legends, are set in worlds very distinct from our own. Probably the majority have known ownership, too, rather than being faceless posts on an image board. In 2021, creepypasta is a massive, varied body of horror fiction self-published online.

When it comes down to it, I don't think creepypasta movies suck because of anything inherent to the format. I've you've ever seen Marble Hornets, an amateur production based off the "creepypasta" character Slenderman, it's interesting, disturbing, and sometimes beautiful in its emotional depth. The problem is really that most mainstream creepypasta films are quick cash grabs, usually trying to throw shlock at a younger audience who are perceived to be less discerning, and often failing to catch the crest of the wave of a character's popularity thanks to the long production times of Hollywood films.

There’s no point in making these movies.