hikermor,
I agree with you that wild plants harvesting has very little return.
I have done it and there are many problems.
Positive id, look-alike poisonous, particular "edibles"
that happen to be poison ( genetics mutation, environmental
factors like soil composition etc.), low yield.

If you are having fun, then do it and use more than one reference.
If I had a friend that was interested,
I might do it again, just for fun.

For sharpening your eye, it is quite incredible; one will be able
to make a tentative id of plants from an amazing
distance. Visit any garden or greenbelt to sharpen skills.

Take notes as to locations.
Some plants are more easily identified before harvest time.
Some urban greenbelts have many native species,
I suspect some are purposely planted.

Small scale farming and gardening is hard, but it is a
cornucopia compared to scavenging wild edibles.

Planting domesticated plants in wild areas: stealth gardening.
From reading the internet, one would think that this is not very
productive. but
I have seen it done, and have done it myself.
I do not mean to minimize the problems, however. It is more
productive that eating only wild edibles, why not do some of
both.

If you live in the city, think of exploring and planting
in the sand right next to creek beds. If the creek is
polluted, you can still do an experiment; you do not have
to eat your harvest.