I understand some of those points. I think one of the aspects is that since every civ is focused on one era, everyone is unique. And since everyone is unique, it almost feels like nobody is. Like, if I'm fighting on my continent with 4 civs, and everyone has a unique infantry unit, sure, they might each have their situational bonuses, but if everyone is special it makes my special bonus feel like less.
And similarly for the terrain. Some of it is that I think the map can be really hard to read at times. The fact that I can barely tell Tundra vs Grassland apart, for example. Or that it's not like the old civ games where your game plays very differently if you're in a flat grassland area vs in a hilly plains area. And then compared to 6, for example, the fact that every city was specialized (overly specialized), whereas now it almost feels like the bonuses vary less. If starting in a Tropical zone you sort of had an incentive to really run down a science path, vs being in tundra knowing that production will be low, but that maybe you'll have lots of happiness. Or maybe desert zones you know that yields are going to be hard to come by, but when you have a wet zone, you can get some big farms going.
I think the game could probably use a little balance by ironically being less balanced. Like, some of the adjacency bonuses just don't seem to matter enough. Does it really matter if I have a +3 library vs a +4 library? One science there, plus half a science per specialist? It barely seems to have an impact all things considered. Sure, every point matters in the exploration when you chase those high yield tiles, but other than that, I feel it just doesn't come into play enough.
I do wonder if maybe the game could have a bit more balance where maybe the base yields are less, but the bonus yields are more. So like for specialists, maybe have them give +1/+1 by default rather than +2/+2, but have them give the yield of the full adjacency. Or even like if you had each specialist have a base yield of +1/+1, but then based on your government, that would apply a different bonus? So Classical Republic gives you +2 culture per specialist, Despotism gives you +2 science per specialist, and maybe Oligarchy gives you 1/2 maintenance on specialists? Or just give me more uneven bonuses - one of the governments can give you +1 culture on quarters per adjacent district, another gives +1 happiness, another gives +1 science?
In any event, I do still enjoy things. Definitely curious to see where the balance changes over time.