Scaring new talent away from spending their precious time on a solved problem like GNU make is a feature not a bug. Work on something more relevant to today's challenges.
There's plenty of things "holding open source back", this isn't a significant one of them IMNSHO.
Saying make is a solved problem is a real failure of imagination. I used to do a lot of work on Blaze and Bazel. I intend to add support for a lot of the things it does to GNU Make. Such as using ptrace() to make sure a build rule isn't touching any files that aren't declared as dependencies. I can't do that if our imagination is stuck in the 80's with all this DOS and Amiga code.
I wrote Bazel's system for downloading files. https://github.com/bazelbuild/bazel/commit/ed7ced0018dc5c5eb... So I'm sympathetic to your point of view. However some of us feel like people should stop reinventing Make and instead make Make better. That's what I'm doing. I'm adding ptrace() support. That's something I asked the Bazel folks to do for years but they felt it was a more important priority to have Bazel be a system for running other build systems like Make, embedded inside Bazel. So I asked myself, why don't we just use Make? It's what Google used to use for its mono repo for like ten years.
"You can't have systemd in Debian, what about kFreeBSD"
"You can't use Rust until it supports DEC Alpha"
...there are no shortage of examples where open and free software is held back by hyper-niche interests, where our pet twenty and thirty year old, long-dead projects and processor architectures create absurd barriers to improve anything.
There's plenty of things "holding open source back", this isn't a significant one of them IMNSHO.