What web technology would you use when dedication is not high?

I am a freelance developer specialized on geographical information systems (GIS). Essentially, I do custom developments involving maps, many of these developments being web applications.

However, web development is not my main activity. Apart of it, in my projects I may clean data, do some spatial analysis, style some maps, tune some database and map servers, etc.. Building a web application is a relative small part of my workload.

This low dedication contrasts with the web technology development pace. I walk slowly along learning curves just to find at the end of it that it is not the right technology anymore. It is hard to obtain a return of the investment when I am doing two to three relatively small web applications a year.

I would love to find an approach that:

* Allows me to build modern looking web applications. Responsive at the very least (Disclaimer: probably I don't know well what a modern web application now is). * Reuse parts from one project to the next. Web mapping applications are not an innovation paradigm and I end up having the same functionalities all over my projects. * Smooth learning curve, long term life. I want to have time to apply what I learn, to build on that and to know well my tools.

In my last attempt I build up a custom solution with a message bus pattern and requirejs modules. Requirejs was on fire when I took the decision but it just got marked as "uncool" few months later (bear with my sarcasm, please). It did the trick for a while though (and still does).

What technological choice would you do in these low dedication conditions?