No, therapists don't need clients. Doctors don't need patients. Teachers don't need students. It is a professional relationship, boundaried and mostly time-limited, with the aim to help a client.

It is not the norm for therapists to be open to further contact, once the professional relationship ends. So, by saying goodbye to them, the professional relationship effectively ended. Truth be told, even if you did have the closure session you so ardently wish for, it would still hurt because you would not be seeing them again. There would still be this void. Then what...?

Finally, self-growth takes as long at it takes, sometimes a lifetime, as long as we keep at it. There is no shame in that.

I don't think your decision was rational, and most certainly not best for yourself.