People who know I forage for mushrooms almost always comment about the possibility of accidentally eating poisonous mushrooms and the impossibility of identifying everything out there. In fact, many if not most of the mushrooms I see in the woods I can’t identify. I can identify a relatively small number of tasty edibles very well though, and a handful of the nasties as well. The rule is to never eat a mushroom you cannot identify accurately 100%.
Fortunately, some of the best edibles are easy to identify. For instance, once you’ve handled a hedgehog mushroom – Hydnum repandum or Hydnum umbilitcatum – and see the tell-tale spines, feel the texture, see the colours, you won’t have difficulty identifying those again. At first, you may just know you’ve found a hedgehog. Later, you’ll realize there are two types, a smaller one with a belly button type indentation on the cap (umbilicatum) or a bigger one with no belly button. The colours are a little different. I find the umbilicatum usually under conifers and the repandum in mixed hardwoods. Both are delicious.
So, how many mushrooms do you really need to identify? Let’s go by season. Morels are a good start. If you find them, you’ll want to harvest them because they are so delicious. They have a couple lookalikes – false morels – but they are easy to distinguish. Then we see the a spring oyster mushroom in our area – Pleurotus populinus. They look like the oyster mushroom s you buy in the grocery store. They have a particular smell and texture – and they are the only mushrooms that look suspiciously like grocery store oysters that grow on dead trees in Ontario in June.
Later, we have chanterelles, a variety of boletes, and then hedgehogs and lobsters (the weird parasite, Hypomyces lactifluorum), honey mushrooms into the fall and so on. My point is that you don’t have to learn to identify hundreds of species to forage safely and successfully. You just have to know a bunch of key fungi very well. I started with chanterelles. My brother showed me some in the forest. I picked a few, felt them, saw them at different stages of development, picked them again on my own, and soon, I was very confident I would not be fooled by any lookalike.
27th Street 
Mr A has the right approach. There are likely a couple of hundred different species of edible mushrooms in Ontario. Part of the whole mushroom problem is that of those couple of hundred edibles many dont taste very good or they have a funny texture or they are never found in large enough quantities to let you make an omelet. There are maybe 20 or 25 or 30 species which are common and which most would agree are quite tasty. You can just ignore all of the rest of Ontario’s 1600 -1800 species of mushrooms. Many folks get all antsy about wild mushrooms and while safety can be an issue it is pretty easy to learn the easy species. If your mom was planning frog legs for dinner and sent you out to catch some frogs hardly anyone would return with toads. That is because they have learned the difference between a frog and a toad. It works the same for mushrooms, you just have to learn which is which and since you really only need to learn a few the job isnt all that tough. One of my favorite mushrooms is the shaggy mane which grows on lawns. When I see some I will ask permission to pick them and it always turns out that the lawn owner has no idea just how tasty they are or how easy it is to identify them. All the more for me I guess.
In his book 100 Edible Mushrooms, Michael Kuo recognizes that there are not 100 edible mushrooms you would want to eat: “The bad news is that while there are indeed hundreds of edible mushrooms in North America there are not 100 good edible mushrooms. We were definitely scraping the bottoms of the edibility and palatability barrels to come up with 100 entries. If you want to eat the devil’s urn (p. 94) or pickled stinkhorn eggs (p.197), have at it, by all means. But don’t say I didn’t warn you!”
I guess using a systematic approach to mushroom identification, as you do, is the only sensible method.
Each year I try to learn to reliably identify a few more. Still, there are some that are just plain hard to identify. Taking the time to do spore prints helps narrow down the identification. Also, there are lots of things to pay attention to…colour, texture, smell, density, staining, shape description of the caps and stalk and so on.