For me, the first few months were the seat that just clicked out of the pram frame and into the car base [0]
After that was a rear facing seat that just sat in the car. Occasionally we'd move to another car, but that's just "unclick, move, click" [1]
Then it was forward facing seats which the kids put their seatbelts on just like adults [2]
What type of seats are you on about?
[0] https://www.pramworld.co.uk/maxi-cosi-easyfix-base-for-cabri... (or similar)
[1] https://www.kids-room.com/en/britax-roemer-reboard-child-car...
[2] https://www.britax-romer.co.uk/car-seats/highback-boosters/d...