Huh? 10 years ago was 2015. Entity Framework had been around for nearly 7 years by then, and as far back as I remember using it, it used source generators to subclass your domain models. Even with "Code First", it generated subclasses for automatic property tracking. The generated files had a whole other extension, like .g.cs or something (it's been a while), and Visual Studio regenerated them on build. I eventually figured out how to use it effectively without any of the silly code generation magic, but it took effort to get it to not generate code.

ASP.NET MVC came with T4 templates for scaffolding out the controllers and views, which I also came to view as an anti-pattern. This stuff was in the official Microsoft tutorials. I'm really not sure why you think these weren't around?