I am slowly digging my way out of the same situation. Here is the skill set I'd be shooting for: * Web development using ASP.NET Core. Including HTML, Javascript, and CSS. (Learn these BEFORE attempting heavy frameworks like Angular or React.) * Docker and Kubernetes. * Basic Cloud technologies such as storage, compute, lambdas, etc. * Learn your way around Linux and open-source tooling. You'll interact with these in the modern world whether you want to or not. * As others suggested, learn what employers in your market want, and develop at least basic familiarity with these. Good luck (to all of us).

Well, and I'm speaking as primarily a desktop developer myself, HTML is one of the very few "common denominator" things that potentially works on anything that has a screen. Now, I wish people in my area hired developers who know HTML/CSS/JS rather than having 20 years in the latest "framework of the week" that causes what should be simple Web pages or Web apps to weigh dozens of GB and to take 45 minutes to load on a mid-range phone over a 5G network.

Well, the metadata is something I find incredibly useful, and this is also why I tend to prefer XML over JSON as well when I need a robust way to transfer data of more than trivial complexity.

For some kinds of very simple data, some dialect of CSV may be ok. But in 3 decades of software development I've rarely found it it be an adequate solution, much less the optimal one.