Here's the current status of .NET software development.

I think there is a broad agreement that unit testing is a very useful tool in developing quality software. Because of the inherent limitation of C#, you can't unit test easily if you don't use DI. This often leads to a situation where you have tons of interfaces + each interface is implemented exactly by one class. This is because product like Isolator is not free. Hyptothetically, if Isolator was provided by Microsoft for free, I am sure that we will see reduced usage of DI.

Don't get me wrong, I think there are other scenarios where DI is a great technique in designing components which are flexible. However, those scenarios are not that many. Using DI to make your software unit testable is an overkill IMHO.