Double the complexity and a rolling compromise.
No it's not. Definitely not. This is a common misconception, especially about Toyota hybrids, and probably hybrids in general. I myself used to think that. But I, like you, was completely ignorant about how it actually worked and why it's absolutely not a rolling compromise. It's a combination of a highly-efficient atkinson cycle engine with a incredibly tiny, electrically-operated CVT. Far from a compromise the engine, batteries, and electric motors allow the car to get incredibly high mileage both in highway driving and city driving, all while maintaining the perceived performance of a much-less-efficient traditional Otto cycle engine.
YouTuber Technology Connections did an in-depth explanation recently, and also WeberAuto has a fanstastic demonstration of how simple and effective the system is.