Not scalable in what way? Every aspect of scalable that I can think of is in no way limited by choosing python as your language.
Mayne that is your problem. Try new stuff. V8 is still one of the fastest and most optimized VMs.
If you reach out to the Java ecosystem you can find libraries, frameworks, and language extensions that make it relatively easy to code in. For example, with Lombok you don't have to write any getters and setters, or catch checked exceptions. Java 11 also makes good improvements to lamdas making method chaining a lot nicer. The Java I write at work is barely more verbose than the TypeScript, maybe 15% more code to do the same thing.
Java devs also get paid really well honestly, pretty sure it's better than the pay for JS and Python actually.
Huh? Rails ships with built-in, no-config webpack support (https://github.com/rails/webpacker#installation) as well as install tasks for the most-popular front-end solutions (https://github.com/rails/webpacker#integrations)
Python not as scalable, Rails is stagnating, the ecosystem doesn't evolve anymore/dying, doesn't play well with SPAs, C# weak to none ecosystem outside of Windows and devs earn a fraction, Java verbose and dev productivity subpar (there was a reason people came up with Scala), Java devs also suffer lower salaries