My filter is usually age. There has been a massive glut of shitty horror in the past 20 years as it's become cheaper and easier to make and distribute independent film.

I tend to look at the 70s and 80s for things have stood the test of time in terms of favorability. Letterboxd is a great resource for that, especially obscure stuff. I'm sure there is plenty of great contemporary horror but I'll stick to things that are recommended to me.