I bypassed the library problem by calling Python from Arc and returning the results as s-exps. It took 40 lines of Python code.

Why not? Have you used a language other than Arc to write a web app recently?

If writing web apps in other languages isn't still painful where have other languages/frameworks caught up?

It's still missing some things that most people take for granted.

One can get libraries for cheap.

Calling Python from Arc with wrappers that return Python data structures as s-exps seems like a workable hack to get libraries in Arc, at least the ones written in a functional style.

Most libraries needed for web apps might be in Javascript.