And a malfunction has the potential to destroy all life in the multiverse.
I didn't like that part at all. An infinite multiverse, which they state in DSC is the case, means that anything with a probability greater than zero is guaranteed. Mathematically, the multiverse should have already been wiped out at some point. It's also a throwaway line meant to increase dramatic tension for all of ten seconds before the scene ends, and an empty threat given that following through would end the show.
Might depend on your area? I mostly just associate them with stoners. Mystic folks in my area are really into crystals.
I meant in terms of 'a thing that links worlds together'. Typically, a trans-dimensional plant or plant-like thing is depicted as a tree, patterned off of the mythic Yggdrasil. World trees are also typically a high fantasy thing, since they're mimicking Yggdrasil. The mycelial network is essentially a world tree, or rather a world shroom. It's not exactly an expected trope in sci-fi. Mixing the genres is definitely doable, but you need to get your foot in the door with some shared concepts before you spring a wrong-genre thing on the audience.
Stamets not being a great vehicle for exposition is definitely a problem, but I think the real problem is that season 1 in general has weird pacing. They spent a lot of time getting Burnham situated on the Discovery and the Mirror Universe arc took up a lot of time for how little actually happened in it. They wound up course-correcting near the end of the season by literally skipping ahead a few months on the return trip. I'm sure it's partially a too many cooks situation with the early show's revolving door of showrunners, but the second season did greatly improve in that regard while still having to swap out showrunners mid way through.
My point is, season 1 is kind of wonky structurally.