I've caught a whole lot of Crappie, long before I ever used electronics. Mostly tied up to a tree & fishing with minnows, but there were times when casting a 1/8oz Doll Fly jig would put fish in the boat, too.
Even now, I'm using my electronics to stay in a specific depth, as I cast or troll my jig or Roadrunner (to fish on or around beds). When that's all said & done, I'll go to casting a jig to blowdown trees or standing trees.
Next time you see people catching them (and you're not) ... just strike up a conversation with them (without getting in the way or interrupting them) and just inquire as to what they're using and why. Learning why the fish are where they are, at a given time, is an important factor to file away in your memory.