You are right. Language is a living thing and the spoken language needs to be practiced in real life.

For some aspects of phonetics I found this book helpful,

https://www.google.com/books/edition/American_Accent_Trainin...

Also, I had help from friends in the comedy world sometimes. I would ask them if I am saying a word right before going on stage.

It took many years but that's because I had to learn it without any books. I was willing to become a child and look like an idiot for a long time.

If I had to do it all over again I would invest time in learning phonetics.