Microsoft does not play catchup in the web space. It is in the pack for some years already. The stuff they do with Blazor is at the upper end of the pack.
.NET, like Java, is not cool. It does not need to. It gets the job done without any experiments in a very modern platform. Doing a startup with boring tech is a thing.
So in summary: .NET is a very good choice for a beginner or converts. It is fresh, you can do solid stuff, do the full stack in one platform (web, desktop, apps, games, iot, ML, ...) and there are plenty of jobs (greenfield or brownfield).