The browser and front end code - just sticking with Microsoft, the popular method has been classic ASP, ASP.Net Web Forms and ASP.Net MVC and ASP.Net Web API and they both have changed significantly after Core. Not to mention that the industry has moved away from server side rendering to client side rendering. The popular client side framework seems to change every year.
The next level down is a server side language, let’s assume that we are doing client side rendering. When I really got serious about my career in 2008, after staying at a job for a decade, job listings were looking for C# and Java. Those are still two of the most popular enterprise languages. While of course both languages have evolved in 10 years, it’s mostly syntactic sugar. If you were in a coma for 10 years, you could wake up and easily understand code in either.
Databases - back in 2001, I was working as a backend developer writing batch jobs to load data into MySQL and Sql server databases and do reports. Now, I’m still working with MySQL doing some ETL as part of my job. What I learned back then is still applicable. The difference between those two databases now and the front end framework of the day is like night and day.
Web servers. I don’t deal with web servers that much anymore (see below), but when I do, it’s still IIS, dealing with IIS hasn’t changed much in 15+ years.
Networking/Infrastructure. I’ve had to deal a little with the networking in the early 2000s, but I didn’t get back into the infrastructure side until two years ago with AWS. Everything made perfect sense. The basics of TCP/IP, servers, load balancers, etc hasn’t changed in decades. While AWS is always adding things, nothing you learn is ever obsolete unlike the framework of the day.