This are just my thoughts; others with much more experience and knowledge will hopefully give you a better answer.
I've never done well this time of year when the fish are transitioning from the deep spots where they hang out in summer back to the shallower areas (at least that's what I think they are doing about now)...I have no idea where they are during this time and have no idea how to locate them. Once they get back in the creeks, it gets a bit better for me, especially if they play nice and let me know where they are by busting shad LOL
As far as fishfinders go, I have 2 on my boat and haven't caught one fish because of either of them yet but I always do know the water depth and temperature