Ironically one project I joined and then worked on for 3 years used Unity, so I was already familiar with it.

Any other reasons you think I might be unqualified to talk about the language I've been using for 15 years?

Just to cover some more bases:

1. I've worked in teams

2. I've worked alone

3. I've made apps from scratch

4. I've maintained large existing code bases

5. I've made enterprise apps, e-commerce apps, BI apps, and even just simple websites

6. Millions of people have used my code

7. Apps I made over a decade ago are still being used today

8. I admit I often forget to floss

Again, none of that means familiarity with DI. Why deflect about the language? This has nothing to do with C#.

You never answered what your actual issue with DI is (the concept, implementation, containers, etc), or what your alternative would be, even though numerous people have asked. That makes your complaint seem largely unfounded or a combination of confusion and lack of experience with DI.

Not the OP, but I never used .NET core, but used DI pretty heavily for most of my 15 years writing C#. It was there before .NET Core. Maybe you mean it's improved with .NET Core?

"wasn't as prominent or included in the framework itself"

There was no built-in DI container before, you had to use your own like Windsor/Autofac/Ninject/etc, and it wasn't as popular because of it as many people skipped it for smaller/less enterprise projects. I'd say exposing more people do it, even if the built-in DI is rather basic, helped improve many new projects that otherwise might not have chosen to do so.