In all fairness to the developers, i watched the initial videos too and i didnt detect a lack of passion.Maybe something like “as little as they think they can get away with” effort is more fair. Probably there was still a good amount of effort, but it seems clear they have a priority to keep it as little as they thought people would tolerate. Even then they did less than people tolerated.
I do think they under-estimated how many people want a huge, open world and under-estimated how many would be put off by a smaller world that feels more linear in terms of gameplay (a common comment in reviews is that the game feels linear/on rails). The impression i got is they went all out for quick and balanced multiplayer games, accessibility and features for min/max strategy players.
I think they under-estimated how many want to play a civ from start to finish, and how divisive ages and the accompanying reset would be. My guess is they felt people would come round quickly as with hexes.
I think the poor UI came from trying to release simultaneously on consoles and PC.
As for predatory DLC - it worked with civ 6, i would guess that they felt that going a bit further in that regard would not get too much backlash, and in all honesty if i loved everything about the game i wouldn't care about the DLC cost.