_ResourcePack is an item flagged by Mod Organizer 2 as a Creation Club item and was included in the 5th of December update, game version 1.6.1130.[bethesda.net]

In the patch notes, the cause of its addition to the game is listed as "to assist Creators".

It can be the cause of crashes If you have tried downgrading.

Either navigate to your Skyrim SE root folder manually, or go to your Steam Library and select "Browse local files" upon right-clicking Skyrim SE and going to Manage.

Once here, the mod should be at the top of the folder, delete it and enjoy Skyrim again!

Thanks to u/NovaVasNasa for this method.

If you haven't downgraded properly, check out this thread.

I personally recommend going through the steam console method, patching didn't work out for me, perhaps because of _ResourcePack still being there.
Also, instead of what Reddit says, Win + R and entering "steam://nav/console" is more comfortable

Also make sure to protect your game from these updates by setting the game to only update when you launch it on Steam properties, so If you use SKSE or any mod organizer you won't have to do this ever again.

May Talos guide you.