This argument doesn't work with Apple. They built laptops that could literally just use 50% of their CPU because of insufficient cooling. Not too long ago they released a Macbook with a CPU cooler that doesn't even have direct contact with the CPU. And when LTT modded the cooler to fix it they realised the performance was still not better because the power delivery is insufficient as well.

Also our PCs are not slow, modular or not. In many cases hardware is not the bottleneck.