Can one of those voice assistant apps be used for this? I don't use any of them myself so don't know (not a fan of them for privacy reasons).
One simple solution is a bluetooth mouse: you need to be close enough to see the pointer on the screen, but you can operate any on-screen control on any app that way. I'm a little doubtful of a generic button-based remote though because that requires that the same button can work the same way with different apps on the tablet, e.g. that you can program a "play/pause" button that works with any video app, which isn't obviously possible (generic TV remotes are different because TVs have a limited set of functions and are designed so that those can be remote controlled. But a media app on a tablet is designed to be controlled via its own on-screen buttons, and so it's not so obvious to me that what you want will be doable).
Yeah, touchscreens in cars are a dumb idea from an ergonomic/usability point of view (just as is removing the instruments in front of the driver and putting all information on the screen in the middle of the dashboard, so that even checking your speed requires taking your eyes off the road for longer). But they are almost certainly cheaper for the manufacturer than mechanical buttons with their own electrical connections, and I'm sure that's the primary reason many manufacturers are trying to get people to accept them.
