As a qualified practising, counsellor I guess I am biased on this topic, but I also have first hand, evidential experience that counselling does work. I've seen it work and been part of numerous people' counselling journey's that have shown me and told me it works, I've also experienced counselling personally as part of my training when becoming a qualified counsellor and so, have experienced change and growth as part of my journey.
What I will say, is that counselling doesn't suit everyone. I do feel this can also be argued a little, because my experience also tells me that the people who I've met (so far) who it didn't suit, appeared to be people that weren't wholly committed to the counselling process. This isn't all the story though and there are other reasons why counselling doesn't suit all.
There is so much to gain from counselling if, you are committed and willing to put the effort in to the process and all it can entail. Commitment in counselling can be looked at as - do you want to do something about the situation that is causing you problems and impacting on your life? whether that is depression, anxiety, stress, family problems, the list can go on. If you do, are you willing to work at it to do something about it?
Counselling is much like a lot of things in life - "you get out of it what you put in to it" and one example I use regularly is; counselling is a little bit like children, you get out of them what you put into them, so if your interaction(s) with a child is half hearted, showing little interest and not really listening and engaging with the child, my belief is that you will get very little in return, they most likely won't talk to you or if they do it may be negative, they will most likely find other things to do and ignore the fact you are around. If however, you are interested in the child, interact on a personal level, show a commitment to the child that you are there and willing to participate in various events and situations in their life, that child will show you love, affection and will want to share their experiences with you, it is such a privilege for a child to hold you in that regard and can be very rewarding. Correlating this to counselling is on that basis, so if you don't give counselling that commitment, by perhaps regularly cancelling sessions, not being honest with yourself in the sessions (which can be difficult - because at the end of the day, the counsellor can only work with what you disclose in the session, you are the person that knows whether it's right or wrong) or not really engaging, then you won't get out of the process the full potential of what is possible. Showing that commitment, engage with the process, being open and honest (as difficult as it may be) then it is highly likely you can completely change the way you feel about yourself and your issue(s). Counselling can help you be the person you want to be, this can be a very positive influence on how you feel about yourself which ultimately results in new behaviours and decision making which you feel confident and comfortable with. Counselling is not about someone else telling you what to do, it is not advice giving but a space to explore and grow - creating clarity and confidence. I say to all my clients that counselling is somewhat counter intuitive because you tend to feel worse before you feel better, but that is also part of the process. Feel free to connect to your counsellor about this, explore this in a session, don't let it stagnate and put you off or drive you away.
Counselling really can be a life changing experience, if you give it the commitment; engage, be open, honest, show courage and be willing to look at yourself in a way that you have probably never allowed yourself to do before. I do believe it works and I believe it can be very powerful with these ingredients.
Another key aspect here is the counsellor, it is not a given that if you do all the above things counselling will work, because you have your counsellor's role as well. A good counsellor will always work ethically and your professional therapeutic relationship will be very important in this process. It's always a good idea to do your research when choosing a counsellor, make sure they are qualified and somewhat reputable, make sure you are comfortable with them, this can be key in successful counselling, working with someone you feel uncomfortable with may cause you to put barriers up that prevent you from being open and trusting. Choose a counsellor who you like to work with, someone you feel relaxed with and at ease will help you with your counselling journey.
Remember we are all individual and unique, one size does not fit all, neither does counselling, it doesn't suit everyone because of how we view things and our own personal outlook on life, but if you are open to counselling and you can be committed then I believe it will absolutely work with the right counsellor for you.