I think you've got that the wrong way around; if you can talk to things using the C library, you automatically get reusability from Java, C#, Python, various Lisps, Ruby, Rust (Go?), and almost every halfway popular language in existence.
What alternative do you know off that is more widely supported by all programming languages?
Vulkan development, for instance, drives me up a tree. Vulkan has probably the best C API I've probably ever seen.
Vulkan support libraries like the Vulkan Memory Allocator all tend to be C++ because that's what GameDev tends to use. And they're an absolute nightmare to integrate with anything not C++.
I mean, even the C++ guys eventually gave up. Look at the proliferation of "Header-only" C++ libraries because integrating with the C++ compiler and linker is simply too painful.
I'm in full agreement with the GP, I just misunderstood the text (that's all on me, he was very clear).
It adds yet another indirection layer on what those runtimes expect, the IDEs aren't prepared for mixed language debugging with anything else, and their build systems also need some additional nurturing.
The problem is that Google is well-known for unceremoniously dumping stuff.
So my first question about any Google tool is: "Does it have enough non-Google people supporting it?" because, if it doesn't, it will die as soon as it becomes a political football.
My second question about any Google tool is: "Are there small projects using it and singing its praises?" Can I use the tool to do what I need to a handful of files after reading a couple of web pages for 15 minutes and have it work. I don't need to scale to 4 gazillion foobars--I do need to get stuff done without an IT staff of 100 people. From a cursory look, Bazel fails that question.
My final question about any tool is more personal: "Does it use C++?" because, if it does, then integrating with anything other than C++ is going to be a gigantic PITA. At this point there are plenty of fine alternatives to C++ that don't suck. If you don't have a clean, pleasant way of talking to things that only understand C library conventions, you fail and I'm moving on.