I think therapy is a process that can vary drastically in length & also in growth, its a very individual thing.
Personally at times I have felt change happening but I've also felt that stuckness that you describe. For me although the stuck part is at times painful and feels like you are going backwards I know that I need to experience it to be able to work on the deeper issues, you've kind of got to dig up all that stuff and work through it before real change is possible- well that's my belief anyway.
So I wouldn't say I have made huge changes over the last 2-3 years of therapy but I can see that I have changed & each little bit of change that has happened is a step closer to one day reaching the point where I feel I am happy in my life. So I do think therapy can bring about bigger change but its very individual. Sometimes what we think we should be working on in therapy is in fact not the real reason for us seeking help- therapy has a weird gift for bringing out or uncovering the needs that have laid dormant for so many years. So although at the moment you may feel as though nothing is going to change, but know it will- it might just look different to what you had envisaged.

Take care
Teddy