It works, if your speech therapist knows what they’re doing. I went to a speech therapist as a kid and she did jack shit about my stuttering. About 2 years ago i started at a new one near my house, and have made big improvements! From stuttering and being unable to hold a convo, being afraid to talk to strangers, i went to being confident in my speech, and able to strike a convo with pretty much everyone! Sure, sometimes there’s a minor relapse, but i don’t let it hurt me. Find a good speech therapist, and you can improve!