At the moment Culture income is just a second 'science' stat with a comparable tech tree that is pretty indistinguishable from the science tech tree in terms of function and importance.
By itself there's nothing linking the culture stat to any real gameplay mechanic that makes it at all distinct from science. At the root of the 'culture' mechanic of prior civ games was the idea that it's a representation of cultural identity and development that was clearly distinct from science, and tied to territorial growth and ideological development.
In civ 7, culture is just 'also science'. Loyalty pressure, culture bombs, border expansion, and having some reflection of the choices you make for your civs development actually reflected in the game in a meaningful way.
At the same time, there's nothing to discourage the player or the AI from just planting settlemens wherever they want with no concern except military vulnerability. Loyalty pressure, culture bombs, and city flipping was a legitimate, interesting, and worthwhile mechanic in previous civ games, and it existed for a reason. Without it, it just feels like the play styles available to the player are just far more limited.
This is compounded by the age/reset system that further discourages cohesive strategic gameplay - and while it was ostensibly implemented to prevent snowballing or something, it does the opposite, by encouraging the player to further lean into wide rapid expansion and relentless aggression.
With no risk to forward settling other than military, just planting a settlement as a forward operating base as close to your enemy capital as you're comfortable with, there's no downside. Loyalty pressure was an elegant way to solve this problem and it is a glaring omission from Civ 7.