Ive never been one to say every single student will get better and hit it great after every single lesson. Improvement can vary with each individual. If you understand what you are being taught, thats good. If (and you def should) hit some high quality, or better, shots during the lesson, thats good also. If you know what you should be working on when you leave, great. If you dont hit it better at all during the lesson....red flag!
Assuming the information is correct for you, progress in different forms should come soon after. Its common to jump back to what you know during rounds. Changes often come with a new set of misses, different curve, different feels, and different distances making it hard to play with. But if you go about it correctly, you should string together a series of shots on the range that were better than before. Then take it out for a test run on the course to try to replicate the feels away from the range when you only have one chance at it. Then start to trust it in your real rounds.
That being said, when someone tries to make wholesale changes, or big ones, sometimes you are asking for trouble during your play season. I only do this in the golf dome in the off season. A good instructor will find ways to creep you along, making you better, all the while allowing you to more easily transition the changes by being able to still play with them. Many just change you just to change you, regardless of your needs.
If you're having the kind of trouble you are having, chances are good either the info isnt right for you or you reeally dont understand it enough to incorporate it. Ive only been able to make big strides when changing something when I have a full grasp of what it feels like and what it means.
Hope this helps