This is true. I had a variety of music lessons as a kid and besides growing a tude, I took away a couple stone fundamentals. That tude needs to evolve into a professional attitude - redundant for this bunch but the other thing is that technical development can't be rushed. More, it can easily be impeded by even the most conscientious of diligence. IOW if you force muscle memory, that's what it learns. Faquen irony man.Finding a straight line and noting I am not cueing straight (which I already gave ascertained) does nothing to help me straighten out my stroke. I already know I have a problem. Correcting it is my challenge.
Anyway the drill:
Lay the stick on the cushion line and just push it back and forth; tracking the line as closely as you can. Don't concern yourself with your arm positions, just watch the stick and track the line. The only wrong is tension. Stop if you feel it. IMO what this will do is ball park your default swing. It'll be easier to develop that than to manufacture a new one.