Well about the 00s and 10s...

To me the 00s mainstream movies took a more psychological thriller turn as opposed to straight up horror. The blood and gore was reduced in favor of darker colors, psychological terror and also computer/online themes, with a kind of focus on teens and young adult audience rather than 'full adult'. I think films like The Sixth Sense, The Ring remake and Final Destination kind of set that tone. It was the last decade where 35mm film was used even in STV productions, and I quite love that look. It was also the decade of a lot of lower budget slashers, with a lot of shadows, stark colors and dark color grading, with a lot of gratuitous up close gore like the 80s and 90s and of course french and japanese films. I also think this decade is more like the 90s than it is like the 10s, with less realism and some out there concepts.

The 10s then to me is about realism, psychology/the mind, meta in terms of connection / allegory to real life experience and also the change in aesthetic due to mostly digital cameras and more natural lighting being used. Movies now seem less "cinematic" and more natural, whereas 00s and before could be way more obviously cinematic in terms of visuals, sound, acting and story. Also can embrace horror in its full embodiment rather than just a thriller vibe like in 00s.

However everything kind of happens somewhere all the time (and never really dies), and in 2010s we've also had the old 90s/00s style horrors like The Nun, The Meg, Happy Death Day, Flatliners, Jigsaw++ and I quite like that style, but yeah it seems to be coming back in 2015+ as opposed to earlier 2010s and never really died, so I'm talking about the actual new movies in these decades and not the continuing of the old.

To me the new 2010s horrors are things like Hereditary, The House That Jack Built, Get Out, Killing of a sacred deer, mother, Annihilation and all of those, which I don't think could have existed in that fashion in the 00s.