This is only true in theory, but couldn't be further away in reality.
Microsoft suffocates everything which is not built in-house 1), so there is absolutely no OSS ecosystem going on in .NET which would allow a choice of different non-ASP.NET web frameworks.
Other languages have a wealth of different web frameworks and some are super basic and lightweight and others are huge with batteries included.
You don't get that in .NET at all. Everything is ASP.NET Core, and ASP.NET Core is a typical Microsoft product - an attempt to build a one size fits all solution, the magic silver bullet to solve everyone's problems at once. Like with all silver bullets, when trying to please everybody you end up pleasing nobody.
1) Except F#. In F# you will find a more vibrant OSS community and non ASP.NET alternatives (most famously Suave), but only because Microsoft doesn't care about F#. Instead of creating an equal level playing field for C# and F# they are morphing C# into an F# hybrid and eventually will stop caring about F# even more than now.