In reality, how reliable is the rotary (or wankel) engine.

All I know is that about 5k RPM you’ll be fine

I’ve unfortunately never driven a rotary powered vehicle, but from what I hear they are reliable if you use them right. That means letting them warm up before revving them high. When they are warmed up, rotaries like to be kept in higher revs than normal piston engines (I heard rotaries that are never revved have much more problems than rotaries that get revved every once in a while). Also rotary engines don’t like short drives, as the engine can’t warm up completely on short drives. And when you arrive at your destination letting the car cool down is also important.

Most of these things are normal for every combustion engine. But for rotaries (and turbo engines) these things are rather important as those engines are more sensitive. So I think the “unreliable” stamp on rotary engines come from the owners who don’t know how to properly drive cars with those sensitive engines. Therefore I would say that the reliability mostly depends on the knowledge and care of the owner.

not very