Depends on the mushroom; certain mushrooms (e.g. beefsteak polypore) are incredibly distinctive, while others require microscopy to tell apart.

One thing you didn’t mention that I think is a major drawback with id apps is smell. If you’re looking at agaricus for edibility, yellow stainers are distinguished by smell if it’s cold and the staining is less obvious.

Other things they can’t use for id are texture (slimy cap Vs waxy etc.), staining (so you know what to look for – boletes it’s necessary to check for blue staining), brittle gills/stem (does it snap?)… All sorts!