Group psychotherapy is an excellent treatment for almost any condition. Indeed, any time group therapy comes up as a treatment option for a specific ailment, I can probably reiterate much of the reasoning I'm about to provide.
Groups let you hear from other people navigating the same problems. You learn you're not alone. You learn to be less harsh on yourself. That's especially important for anxiety sufferers, who become a little anxious about something, then become really anxious when they become anxious about being anxious. Learning to get rid of guilt and shame, or at least to not let it control you, can short-circuit that vicious cycle.
Groups let you see others successfully navigating the same problems that you have. They show you that you can get there too. You pick up tips.
And groups allow you to share your frustration with others who will intrinsically understand.