The 3rd gen RX-7 is commonly called the FD (1st gen is FB, 2nd gen is FC... having to do with the chassis code on the VIN). It had a complex twin turbo setup with one small turbo for the low end and a larger turbo for high end power. The car had beautiful styling, handled amazingly well, was fast, etc, but due to some poor design with heat management, the engine would easily overheat, and it was rare an engine lasted 75k miles without grenading. Prior to that, the RX-7s had a fantastic reliability record, with many lasting over 250k or 300k miles. The FD made people doubt the rotary engine, label it as unreliable, and effectively end its production until the RX-8.
BTW, complexity? The rotary? The rotary engine is incredibly simple- it has 3 moving parts.
It's pretty easy to understand.