I do not agree with your generalisation, the Meson build system is well thought, it has a clear declarative syntax that let you just express what you want in a direct way.
The designer of Meson explicitly avoided making the language turing complete so for example you cannot define functions. In my experience this was an excellent decision to limit people tendency to write complex stuff and put the pressure on the Meson developer to implement themselves all the useful functionalities.
In my experience the Meson configuration are as simple as they can be and accommodate only a modicum of complexity to describe OS specific options or advanced compiler option one may need.
Please note that some projects' Meson file have been made complex because of the goal to match whatever the configure script was doing. I had in mind the crazy habits of autotools to check if the system has any possibly used function because some system may not have it.
Meson is way better than autotools, but if you're too level to depend on python, you're probably needing to customize your build scripts in the ways you mention. I don't see meson being a silver bullet there.
Also, meson's build dependencies (muon, python) are a lot for some of these projects.
The designer of Meson explicitly avoided making the language turing complete so for example you cannot define functions. In my experience this was an excellent decision to limit people tendency to write complex stuff and put the pressure on the Meson developer to implement themselves all the useful functionalities.
In my experience the Meson configuration are as simple as they can be and accommodate only a modicum of complexity to describe OS specific options or advanced compiler option one may need.
Please note that some projects' Meson file have been made complex because of the goal to match whatever the configure script was doing. I had in mind the crazy habits of autotools to check if the system has any possibly used function because some system may not have it.