You can buy Volta GPUs on laptops. There are just none that are as weak as the GPU in an M1, because it's an awful niche where you're neither fast enough to really start using the GPU, nor slow enough to do away with it entirely. There are GPUs with that amount of performance/watt available. There are even some in really thin laptops. Go looking, PCs have evolved since 2012, Thinkpads and Macbooks aren't the only thing that exist anymore.

They are much better than what Macs used to be. That makes them middling. There is no real performance advantage of M1 Macs - least of all in GPU performance - over the current AMD/NVidia standard, and quite a few disadvantages.

What it really is, is Apple making their own processors to be able to lock down their Mac platform really harshly and have total control over it, without offering any performance advantage over their competition, and people spinning it as actually a good thing because Apple had the good sense of making their previous generation of laptops worse than it had to be to make modern hardware feel revolutionary.