I like the idea of the mycelial network at its most basic core concept, but it's execution or delivery in Disco S1 is literally what killed that show for me. I started a rewatch of Disco S1, in the spirit of confirming my theory that nu-Trek peaks in the first seasons (because, I'd guess, it's produced more like a Trek film than Trek TV show) ... and I couldn't get past the episode (3 or 4?) when all the details of the mycelial thing drop. Doing it in a prequel also did not help for me and I'm still not sure the way they've "prevented" it from showing up later in-unverse holds up at all.

Romulan stuff was cool I agree. Jurati borg too (after TNG, the only borg ideas that were compelling I'd say were sort of borg adjacent phenomena as occurred in Voyager a couple of times). The Trans-warp conduit seems to me a lesser version of the EGS though ... combining Jurati Borg with EGS and getting them to interact or something could be an interesting sci-fi arc.