In a way, I do think it's true that a therapist may not work very well with a client who is much more open-minded or experienced than him/herself. A therapist who doesn't know their own issues and blind spots very well may very well block the client's process.

That said, I think this is a but dismissive about the client's participation. The client needs to be open, willing, and prepared to go where the client wants to go. It's not just up to the therapist to "take" the client somewhere. It is the client's journey. In my opinion, the therapist can just provide a healthy, good context and relationship, perhaps questions, interpretations or whatever their chosen method offers. But whether the client can and wants to grow is a different question. So I don't think the therapist's experience has to be a limit - after all, no therapist can have processed everything or experienced every issue the clients may come with. But I do think the therapists' own journey is vital so that the therapist can provide a safer context for clients, free of their own personal conflicts and issues.