Compared to many other ICE cars, Toyota hybrid drivechain is relatively simple. There is no turbocharger, no double-mass wheel, no starter engine, no DPF, the transmission has no other moving parts than just a few rotating planetary gears (constantly engaged), no clutch, no microclutches, no momentum converter. There are fewer moving parts than in a manual transmission, and forget any other classic automatic transmission. E.g. in comparison, DSG complexity is atrocious (and unreliability famous). In exchange there are 2 electric engines and a battery - but that’s all quite simple and reliable technology.