For shared project types (other project types don’t have this issue) when selecting the “Add Class” menu item:

I don’t get the standard C# class items, I get MSBuild Directory.Build.props file and MSBuild Directory.Build.targets file templates:

How do I change it so that Shared Projects open with the default Add Class C# templates?

I found this documentation on how to add items to the dialog: https://learn.microsoft.com/en-us/visualstudio/extensibility/internals/adding-items-to-the-add-new-item-dialog-boxes?view=vs-2022 but it looks like it is only for adding your own custom templates, not for configuring which template group to show.