That is, not every project has "shortening ramp-up time" as a priority. In quite a few cases non-trivial code doubles as filter for less skilled devs.
An OS kernel is going to be a very complex piece of code (ignoring microkernels) because what it does is complex. But that is all the more reason to keep the code as straightforward as possible. (There are still going to be times where code is not straightforward due to inherent complexity of the problem, or performance considerations, or portability, ...)
Right, until the less skilled dev it's you, months later after you moved on to other stuff, and have to get back and fix some clever shit you wrote but don't understand anymore.
Unless you're doing numeric or performance critical work, code should be optimized for readability and maintainability.
I was talking about the more broad idea of knowingly writing clever code to raise the entry barrier for new devs. Or just writing clever code for whatever the reason. It's almost guaranteed to backfire, to new devs who will have to maintain it or to yourself, when you will have to read it in a less smart moment.
Also, "less skilled devs" are just people that are still learning. We've all been there.
Projects should be accessible to new developers with appropriate skill set, which is inherently defined by the projects' complexity.