The animation of the passengers entering the bus was done during the development phase. The problem that TML removed this feature in the release version.
I know this because in the first videos a year before the launch, some passenger animations were shown.
It was a demonstration of the bus arriving at the stop and the passengers entered. I don't know why it has not yet been implemented in Fernbus and the feature is present in the Tourist Bus.
Another thing they removed from the game was the passengers walking the streets after arriving at their destination. Currently passengers are stopped at stations. People who arrived at their destination have to walk, some may stay put, maybe they want to take an Uber home or are waiting for someone.
But I can't even complain too much because the latest updates are adding good resources, TML's team is working hard on this last year so far.
More I agree that this is something basic and should never have been absent for so long.
At the moment I am really waiting for the vehicle sounds to be updated, I want something close to the reality of each vehicle, Fernbus will be celebrating its 4th birthday and these generic sounds are already tired, unacceptable.