i tried using torches on it but that didn't work. i don't have good enough gear atm to just run straight into the loot center thing, but i can't figure out how to stop the spawner. i also don't want to break it because it's super close to my portal. if anyone knows how lmk, thank you! : )
I don't have any experience with them but I'd try filling the area with fences, 5 blocks out from the spawner if it works like others, starting at the entrance and working my way in. Fences made from the new Nether woods should be fireproof.
Mixing fences and walls should make it easier to leave gaps through which you can fight, place more fences/walls and move closer.
Or maybe solid blocks and fences, a fence diagonally next to a solid block leaves a gap that cave spiders can't get through so that should work for even small cubes.
Once you have the spawner completely fenced in, 5 blocks out, you should be able to ignore any new cubes that spawn since they should be on the inside, just leave some gaps to reach any chests and kill cubes through.
Or, if you can start at the ceiling, you could fill the area with gravel, 5 blocks out from the spawner and 1 block above it should be enough to block all spawning spaces.