If you want GPU performance to match a dedicated GPU, you can't fit it in a Macbook (or any Mac except the Mac Pro, for that matter). Even if the M1's graphics units only used 50% as much power as an equivalently-powerful Nvidia or AMD dedicated GPU, putting enough graphics power onboard to match even a midrange GPU would immediately overwhelm the cooling abilities of the computer.

Apple could absolutely choose to make better cooling, but they've demonstrated time and time again that they'd rather just let thermal throttling happen and trust that their users will continue to buy a product that doesn't live up to its spec sheet's promises.

Any cooling that could support dedicated-GPU-level performance would require making the chassis dramatically thicker - take a look at some of the gaming laptops out there today with desktop-class GPUs, they can get be like 2 inches thick in pursuit of cooling good enough to support a full-power GPU without massive throttling.