Why didn't you concentrate on the main quests then? I had a similar issue with NieR: Automata recently, where all the side stuff was just boring to me. So I concentrated on the main story and enjoyed it much more this way.
I did in the end but it took me a long time.
I'm one of those people who likes to exhaust every dialogue option and when I come to a fork in the road do my best to try and go down both paths. I'll take my time and explore nooks and crannies in even in the most linear "walk down this long, straight, corridor" type games and it drives my brother fucking NUTS when he watches me play anything.
At the start, I was enjoying the combat and the visuals so much that I was happy to go around trying to talk to every single NPC to see what would happen. Then I ran into the encumbrance limit and abysmal inventory management so I made it my goal to try and upgrade my resource limit ASAP so off I went hunting. While I was at it, I figured I may as well increase my quiver size and the rest of the equipment upgrades so I spent ages hunting various animals, all the while thinking I couldn't wait until it was over and "Far Cry did this better, at least those honey badgers could fuck you up."
Got all that done, got started on the hunting lodge challenges and did some side quests and it dawned on me that the game was trying it's best to make me dislike it so I bit the bullet and smashed through the rest of the main quest.
I think I can trace it all back to Dragon Age Inquisition, that was the game that really made me hate open world padding with a passion. Horizon doesn't come anywhere close to that game but I am more acutely aware of the bullshit that comes with most open world games nowadays and I really can't be arsed with it.
It's why I'm disappointed with Horizon as much as I was impressed with it, because it's an OK game with some unbelievable high points. I felt like I was pausing the game every two minutes to go and dick around in photomode and like many people have said, the machine combat is incredible.
My big beef with the game is all that other shit which gets in the way of the awesome stuff and drags it down. Like, if I had never played Far Cry 4, Rise of the Tomb Raider, Dragon Age: Inquisition or a bunch of other open world games then I probably would have loved the game. As it stands though, I have played all those games which means there was no escaping the "Oh, I climb a tower to uncover parts of the map", "Oh, I'm going to be collecting these branches that stick out of the ground every 100 metres aren't I?", "Time for a half-arsed hunting challenge or fifteen".
Horizon isn't a bad game by any means, I enjoyed quite a lot of my time with it and I don't regret playing it at all. I'm just a bit more vocal in my criticism because I think of what it could have been and I'm disappointed. It would honestly have been one of my games of the generation if they focussed even more on expanding the combat and not felt the need to add things just because every other AAA open world game seems to have them nowadays.