> I just don't like his arguments about it must be fast to recompile everything.

C isn't necessarily fast to recompile everything. Too much preprocessor magic and the compilation can slow down a lot.

And a lot of the reason for that, is that C's preprocessor is inherently weak – e.g. it doesn't explicitly have support for basic stuff like conditionals inside macros – but you can emulate it with deeply nested recursion – which blows up compilation times enormously. If C's preprocessor was a bit stronger and natively had support for conditionals/etc, one wouldn't need these expensive hacks and it would be a lot faster.

Example of real world project where C preprocessor slowed things down a lot is the Linux kernel: https://lwn.net/Articles/983965/