It's not really difficult to implement your own animation class using the tools SFML provides, that and you can tailor it more specifically to your own needs.
It's important to remember that libraries like SFML insulate you from the task of learning lower level stuff like OpenGL, in detail, which in itself is a lot of research.
By comparison, an animation class created using SFML is pretty easy because, well, you don't have to think about so much stuff. Just use the library as a go-between, which is what it is.