Not everyone is working on projects that are little more than CRUD webapps. I've worked on code that took hours to compile even on beefy machines.
At the other extreme I've also worked at Google and have seen insanely complex C++ code bases compile in 30 seconds flat.
Multiple hour build times usually show that nobody smart enough had the interest and authority to solve the problem properly. It doesn't generally mean that your project is awesome. It certainly isn't something that I would brag about.
Also, sometimes it's not about code, it's about digital assets, which is going to be IO bound. I've worked on projects that took a full working day to do a clean compile and others where it was necessary to do binary integrations instead of code because the overall build time would otherwise be measured in days or weeks.
Your CMake makes incremental builds safe, and the ccache saves you when switching between branches.
Also from what I've seen, large header-only codebases tend to be external and thus generally don't change that much, so if you can limit your own internal dependency tree ccache can still save you.
I've seen tens of thousands of lines of code compile in 30 minutes.
I've seen a hundred thousand lines of code compile in 2 minutes.
It really depends on how the project is laid out. If you're using lots of header-only libraries and try to compile monolithically (like soooooo many C++ applications do these days), you're going to have a bad (compile) time.
Of course part of the trick is that work has been distributed across a cluster, so a lot longer was spent compiling than that...