The marketplace isn't operated on a paid contract for vetted extensions. You vet the extensions you use. Most don't, and it's ok. Don't shift the blame and the cost on microsoft though, they don't have to offer it.
Raymond Hill (of ublock fame) wasn't really impressed with how it is performed, but it's still much better than nothing (which is what MS apparently does).
VSCode is an IDE in name only, it's a glorified text editor, and pretty mediocre one at that. I in "IDE" stands for "integrated", like what you'd expect from JetBrains' products. Or even the real visual studio.
Or to make things more succinct:
* VSCode is a extendable code editor (like vim, neovim, Zed and Sublime)
* Jetbrains Rider is a fully equipped Integrated Development Environment (like Microsoft Visual Studio or its direct sibling Jetbrains IntelliJ IDEA)
And while extensions are optional within a IDE (and often solely used for increased productivity), more often than not they are a necessity in a code editor to even become productive.
"Integrated" isn't meant to contrast with a plugin-based system (otherwise JetBrains wouldn't count!), it's meant to contrast with a dev environment built out of a bunch of individual tools and terminal commands run separately.
How you know that?