The basic problem with Wankels is that the geometry of the combustion chamber (such as it is) is constantly changing, which inevitably results in incomplete combustion compared to traditional ICEs. This leads to lowered fuel efficiency and greater emissions; the emissions problem is solved with an additional combustion chamber for the exhaust gases, but this consumes more fuel and lowers efficiency even more. It’s just a fundamental problem with the technology that no amount of development could ever fix.
The basic problem with Wankels is that the geometry of the combustion chamber (such as it is) is constantly changing, which inevitably results in incomplete combustion compared to traditional ICEs. This leads to lowered fuel efficiency and greater emissions; the emissions problem is solved with an additional combustion chamber for the exhaust gases, but this consumes more fuel and lowers efficiency even more. It’s just a fundamental problem with the technology that no amount of development could ever fix.