> In Amsterdam, trams stops have a platform for people to get on and off. Is that not a thing in other cities?

Almost everywhere platforms in Zurich, but with very few exceptions.

> Also, if the tram stops cars, then cars also stop the tram, which means delays when car traffic is stuck.

Trams in Zurich steer the traffic lights (TF) => when a tram nears an intersection the TF will switch to let it pass and when it nears a section of road which is shared with cars that occupy it, the TF in front of the cars will let cars in front of the tram pass to free that section of street / lane so that the tram can pass as well.

Jams can be caused by more than just traffic lights, though. Control of traffic lights is not going to solve everything.

I did not write about the cause(s) of traffic jams nor about controlling traffic lights to solve anything. My post was about "trams", not cars.