Plz is great for c++, and has a better workflow (IMO) vs (e.g) Cmake. The skylark-like syntax is easier to reason through than cmake generative expressions. Also the use of “plz run” vs “cmake -g; make; run”
cmake generator only needs to be run once per project. After that you use make or ninja directly, and it regenerates the build files if necessary. I can't say it's a strong argument against cmake.
This added user complexity is exactly the argument for plz, though.
One of the ideas touted is (to my mind) tight integration, in that plz knows how to handle everything. Whereas cmake just makes project files and leaves it at that.