Okay, I fixed this issue on my end. No idea if this will work for others but I'll share just in case.
1: open Steam.
2: right click Skyrim and select "properties".
3: select "local files" in the properties window.
4: click "verify integrity of game files".
if the files are corrupted or messed up in any way, it'll fix them automatically. wait for Steam to download the fixes. this WILL update your game though, and if you're not interested in running version 1.6xx, I highly recommend this patcher to revert to 1.5.97
(download the first option, the full patcher. I dunno if the "best of both worlds" option works and haven't tried it, so I recommend the first option.)
download MANUALLY, not with a mod manager. unpack the fullpatcher.exe into your Skyrim SE root folder. click it, run it, and have fun with Skyrim.