I agree wholeheartedly with all you have said. Also that Sins1 although a great and unique gem oif a game, but that it got stale fast. I could only play one complete game of it every so often because of the repetitive nature of the late game and the face that the game pretty much played the same every single time in terms of research and battles. It was blob wars with the largest blob winning.
I've said elsewhere i'd loved sins to take stellaris's research tree and ship building system. Which at least adds a little more in the rock paper scissors department without it feeling as formulaic.
Total War? Yes I too think that sins2 would benefit from a little more life. But rather I don't think the solution is more traffic in the gravity well, but more personalities as leaders of ships and planetary governments etc. I'd want to see some personalities come out of characters experiences in game. Promotions and even traits gained as their home planets get raided and such. The static portraits are not doing it for me. Nor is the super sparkly pastel colour pallete. You could even transport personalities between planets on envoy ships to new roles on recently conquered planets.
Don't get me wrong, I'd love to see more traffic and events happening in gravity wells. But I cannot see it happening due to the assets and performance issues they would bring. What do you want to see? Starliners, science vessels, tourist vessels, offworld colonies etc? I think more what needs to happen is for us to see people animating things. To see faces move and talk? In stellaris they had cartoonish animations for things but they made things worse as they took you right out of suspension of disbelief by being so goofy.