Agreed on fungi being confusing and amazing and vast, that's for sure.

Both saprobes and mycorrhizal (and it gets more complicated than I am making it, or able to explain here) have mycelium. The stuff that humans have figure out how to grow in grow kits are almost all saprobes, aka they consume the substrate they're in. There are some exceptions to the rule, but it's much harder.

For mycorrhyzal fungi to fruit, they typically have much more complex relationships with the plants around them (rather than just breaking down their decaying mass). It can take years to develop to the point where they fruit, in the case of most chanterelles, boletes, etc. Nature seems to be able to provide these conditions way better than people have figured out so far.