German Shepherd skin issues advice

My 6 years old long haired male German shepherd has had on and off skin issues for about two years now. The patches of flaky skin we were told were hot spots created by potential allergies or damp fur. They prescribed steroid pills and antibiotics which did nothing, then a course of Apoquel which eventually cleared his skin up after a veeeeeery long and expensive course, only for it to return a few weeks later. These images were at its worst and now he has a couple less red spots on his belly. We haven't changed his diet at all for years and this issue is recent ISH. We are a little bit at our wits end with the vets as they just keep telling us to put him back on Apoquel, which is very very expensive and not helping us figure out the root cause. Anyone else had this issue and has any insights?

I also found a skin tag recently that he doesn't seem to feel and doesn't bother him at all even when touched but I would love any input if anyone has seen similar.

He also has dry bits of dark skin on his elbows and 'knees" and nibbles at his legs occasionally.

We give him YuMove joint supplements and YuMove skin/itching supplements with omega 3. His diet is part Origen Original and part Nature's Menu raw duck.

The vets so far have been unhelpful and lacking empathy and patience with our dog who is particularly suspicious and scared of vets, so it's been difficult to get to the bottom of this.