You seem to use sentience as a synonym for human intelligence. Works, accomplishments, cooperation: if you don't see those things when you leave the city, you're (forgive the hyperbole) blind.
But its all consistent with vegetable blind optimization for their environment.
As for social organization, works, cooperation - the fact that they grow in a group and are impressively big says nothing about their sentience.
"In soils across the world, fungi trade resources with the plants they colonise in a mutually beneficial relationship. But it turns out the fungi are savvy traders, taking advantage of their partners by shuttling goods to nutrient-starved areas where plants are willing to pay more than usual"
(from https://www.newscientist.com/article/2205604-brainless-fungi...)
FYI. Sort of relevant.