As another adult starter, I'll just say that 30 minutes a day is probably (!) not enough for an instrument with such a substantial "learning curve", no matter how strict or rigorous the teacher is.

If you can't carve out more time, the stricter teacher will be a waste since they will expect things that will need more practice time to do.

How about these questions to your current teacher:

What can I do to play this piece better?

What are you doing different when you play this piece that makes you sound better than when I play it?


There are actual discussable answers to those questions. (Beyond "practice more")

I'm presuming you don't already have answers to those questions.  If you do, then you know what to spend that increased practice time on.