It doesn't work because of energy loss converting mechanical to electric and back is higher than mechanical transmission straight to the wheels. Honda does do s

It doesn't work because of energy loss converting mechanical to electric and back is higher than mechanical transmission straight to the wheels. Honda does do something like what you describe at low speeds but the efficiency is not very good. Toyota and some other manufacturers use clever arrangements of planetary gears + motor/generator to keep the engine closer to optimal parameters independent of wheels. I'm not sure a modern hybrid system is more complex than a modern automatic transmission.