That's simply not true, as people have found out, having eaten the wrong plant in error -this is especially true with fungi and there are several poisonous wild plants that can be confused with edible ones.

By the way, there's no difference between mushrooms and fungi.

I think this has been answered, but I'll chime in too.  Not everything growing in the wild is good.  Some of it is downright dangerous.  If it were that easy, no one would offer courses in how to survive in the wild.

Also, I would hope that you would not wait for the 'young english wife mother type' to show up to prepare food for you--you could starve to death first .  I suspect that if faced with starving to death, and figuring out how to get the fur off a rabbit, most of us would be able to get it right.  On the other hand, if you've never seen offal--that could very well confuse people!

Shelter and water are still the two most important things to obtain though...

Kingfisher