Fishing without electronics isn’t like it was when I was a kid (I’m 44). Not many had them back then and topo maps were limited. Nowadays, I’m guessing over 75% of people have flashers, if you have a smart phone you can get topo maps for cheap, and the fish have pressure they’ve not had historically. THat said, it will be more challenging to get on certain species of fish.
In my findings, northerns are easier. Find the weeds, find the northerns. Walleyes won’t be as easy, but not horrible. Use a topo map and a GPS to get close to the structure, punch holes and find the right depth/area you want and you know that 95% of those eyes will be on the bottom foot or two. Panfish and crappies will be much harder though.
All said, I would try to find a used flasher and make your experience much better if you can afford it. Can you catch fish without one…yes. But not remotely close to the numbers if you did have one….even an older one.