Really curious what is actually wrong with "crude bash scripts for building"?
I had experience with both types of projects - the ones with home made crude build tools (in Python, not bash), and the ones with modern javascript build pipelines. The first build never broke. The second build would break every couple of months for no obvious reason without us touching the project structure.
There's nothing wrong with handwritten scripts. The lack of problems are exactly why the current dev workflow has scaled and I'm saying this as of 2019, which I find interesting!
The problem is opportunity cost. The rest of the tools in the market (Webpack, Rollup) are offering heavier benefits like automatic code splitting, dead code elimination and such things.
The equivalent "modern" workflow is written, owned and optimized by build brainiacs with turnover on the order of weeks. I'd say that maintenance of "crude shell scripts" is much less difficult and expensive than keeping up with the latest webdev "standard practice".
You'd be wrong. I'm not arguing that Webpack is a deeply confusing system, but there are tens of thousands of people out there figuring it out too. Almost any question has an answer a Google search away.
I had experience with both types of projects - the ones with home made crude build tools (in Python, not bash), and the ones with modern javascript build pipelines. The first build never broke. The second build would break every couple of months for no obvious reason without us touching the project structure.