I'm confused on whether you should still use controllers in your ASP.NET Core project if you are using Razor Pages, since they removed the pre-made controllers folder in the Razor Pages project type.
I'm using Razor Pages, Entity Framework Core, and SQL, fi that matters.
It is up to you. There are people who still use controllers in ASP.NET Core 2+ because they do not like the idea of Razor Pages. You can have both of them in the same project. I personally like Razor Pages, but I still use Controllers when I have to make an Ajax call in order to get data from the server to update the contents of the page. For Ajax calls I also use the Razor Page by defining handlers to get the data.
Controllers also can be used in a Razor Page project in order to create web services so that other applications are able to retrieve information from the Razor Pages application.