We can't all be plants and fungus.
I think it is possible for life to evolve on a planet with only plants and fungus.
Plants have been pretty successful down here on Earth, and I think most of them don't need animals for their survival (except flowers?).
That's kinda circular, given that plants and fungi are examples of evolved life :)
You are correct that plants don't strictly need help with pollination (they simply release their spores to the wind/current and hope they land on a receptive partner), however the odds of a succesful pollination decrease sharply as the number of competing plants in an area increase.
In my (uneducated) view, in a scenario where all life is stationary (rooted to the ground, hur hur), you are much more likely to find monocultures -- where most plants can interbreed -- or more species using asexual reproduction.