The moia service in Hamburg Germany offers virtual stops which is the next step I would argue. The bus follows a different route and stops every time based on the need of current passengers
In the UK/London there are some bus routes where you just stick your arm out and the bus will stop to get you where you stand ("hail and ride") and equally you can just ring a bell when onboard and the driver stops as soon as there is somewhere convenient to let you off. The route is fixed though.
Is it that sort of thing?
[1] https://bus-routes-in-london.fandom.com/wiki/Hail_and_Ride_b...
I guess this is what you call "ride sharing". It is like your parents picking you up from football and realizing the kid from the other part of the town also needs a ride so they make a huge detour
That variability makes the whole system much less interesting once a change is involved, e.g. if the on-demand shuttle is only supposed to operate across the local area, but not for longer journeys traversing the whole city, especially if the connecting fixed-route transport runs less than every few minutes…
Or even without changes, but when you have some other external schedule constraints, because in those cases you always have to budget for the longer journey time, negating the benefit of direct routing somewhat.