I would not worry about your age so much, and the maturity can even help you.

I started my Ph.D. at 26, and took a long time to get it (at 32.. 6 years), but it really paid off. I now have my dream job in research industry, and putting all my training into very good use!

You might be able to start a more theory oriented ML topic and switch later if you are not liking it. I switched supervisors and topics two years in.