Interfaces in C# are used way more often than abstract classes and inheritance. It is also becoming more important as there is more code written in Rust style with structs implementing interfaces for zero-cost dispatch through generic constraints e.g.

    void Handle<T>(T value) where T : IFeature1, IFeature2...

In C++, you can use C++20 concepts[0].

[0] -- https://en.cppreference.com/w/cpp/language/constraints