It's not too hard to pick up new tech when you've been in the industry for a while. You can even do it on the job with some afterwork study.

To me the problem is the emphasis some companies place on knowing specific tech.

>Must have five years experience in Web development with a focus on front end frameworks eg react/angular and cloud experience (aws preferred)

VS

>must have two years experience with the following; asp net 5.0, aspnet mvc 5.0, automapper, xunit, tiny ioc and azure Webapps

However, typical the good companies have the former. So you can spot it out pretty easy. Although I fear the industry is moving more to specific skill sets and certification. The certificates trend is being pushed harder as it makes a lot of money for these companies.