You raise some valid points. However, there are an abundance of edible plants that are readily available - cattails, oaks, pinyon pine (in the west), dandelions. The catch is that much of their bounty is available only seasonally (except for the dandelions in my back yard). Many edible plants are distinctive, even for a botanical dunce like myself.

A key concept is to broaden your horizons in terms of what is edible. I understand rattlesnake (and probably just about any snake) is delicious. All you need for them is a nice big rock.

I am in luck living near a rocky coast. Lots of intertidal invertebrates are readily available

The key is attention and observation before the situation becomes crucial, just as you are doing. Bon apetite!