Difficult tailwater fishing. Any tips? -Trout

Hey guys, i live in Norway and this huge river is next to where i live. The stretch i'm usually fishing is in betwen two dams. This stretch of river contains the pickiest trout i've ever encountered, but they're big! I get completely skunked 8 out 10 times when i'm fishing here which kind of motivates me to want to "master" this river stretch.

The river is deep and wide with a really slow current and it's right next to a road close to the city. So a lot of people have fished here, which is think might be part of my problem. I suspect that the fish here has seen every variation of baits.

Like i said earlier, i rarely catch fish here but when i do they're pretty much always 1KG or more, biggest i caught was 2.8 KG which kind of makes up for me getting skunked so often.

I've tried everything. Jerkbaits, spoons, spinners, pencils, flies, slow fishing, varied fishing, fast fishing, flashy baits, dull baits, matching the colour of water, longer leader, thinner leader, upstream, downstream, shallow, deep, mid water, changing locations.

I feel like i've tried it all except a bottom rig which is what most people use here, but i find it so boring that i can't make myself do it.

Has anyone else here encountered this problem? Am i just fishing the wrong spots you think?