As far as I can tell, all the mod builds for the same Fallout 4 or Skyrim are located on sites independent of the same Steam. As an example, torrent trackers. Over the past 10 years, I've downloaded a couple of terabytes of these mods (mostly in the form of ready-made builds), without ever paying a dime for it. Therefore, I consider it stupid to create panic. But if you play by the established rules and pay for downloaded movies, TV series, and games to some companies/corporations, these are solely your problems.
Oh, yes, I forgot, you can get your ass kicked because of the content on your PERSONAL computer...
This is a problem of mutual relations between you and your government. You voted for them. Now enjoy it.