That is really odd. Research will be required.

from what I've seen anyway. after deactivating this asset, the Classic mod worked again

the only mod this hurts is the clasic mod. Due to custom contents in all of the mod completely changing how the game looks

This is an addon and thus is restricted to asset types that should not be able to cause bad-assets. I know for a fact this addon won't cause bad assets. Also, the game's asset system should not have bad assets from a mod unless the mod is out of date or there are custom contents in addon in your local install. If the joiner is receiving a missing mods error however that's a different problem.

i recently joined a game with the starfleet mod and got it automatically downloaded in the process. i dont remember who it is now. they might have been testing it. but unfortunately no one else can join my starfleet game. always says bad assets.

That's okay. Battlezone veteran since 1999 here. I'm patience

I think someone is working on porting and updating Starfleet based on comments in the discord, but it could take some time.

is it yet possible to find the actual Starfleet Mod?