I remember seeing these kinds of single-file web apps when I used PHP ~15 years ago. It was a good time! Unfortunately, no such culture seems to exist in other web language ecosystems.
The PHP era, with all its flaws, brought an insane amount of productivity compared to previous solution (eg. Java).
I can't quite pinpoint what was the cause but I've never been as productive as with PHP + JQuery.
Modern tooling is just plain slow, mandatory and definitely gets in the way. Having extra layers means more bugs you waste time on and bugs that are harder to debug.
It seems like there are also less and less tutorials and documentation.
