Leyrann
Deity
where others said that era points are mostly random
I don't know who said that, but that's not true. You earn era score for quite a wide variety of things, and it's also just a game mechanic; even if it has a high flavor aspect doesn't mean you can completely ignore it and still play the game as if it doesn't exist.
If you really dislike it and don't want to have to take it into account you'll have to disable R&F.
My main complain aboyt the loyalty system is not this anyway, but that I need to go full war and capture all cities,
That's not the case. If you take the right cities and make sure you're not fighting with dark age versus golden age or something like that, taking one or two cities is arguably the easiest way to conquer - on the condition they're close to your borders. Remember that even if you don't win in loyalty before you conquer a city, once you conquer it you get the loyalty boost from it's own population, rather than the previous owner, and on top of that you can put in a governor to give another significant boost. And, of course, you might want to keep a unit in there to not get a loyalty penalty for the city being occupied.
There's plenty of things wrong with war in Civ VI, but this is certainly not one of them.