[pjmlp]

Except for the little fact that in the 80's and 90's most hobby coders still managed to write better Assembly than C compilers for home computers were able to generate.

C compilers are fast in modern times, because of the amount of industry money spent in writing C optimizers since the industry adopted it.

[slededit]

You can still write better assembly today. You just probably wouldn't be able to keep up the effort for the entirety of your code base.