It's their knowledge and experience that lets a strong player (after a lot of work) definitively say ____ is a good line and _____ is a bad line. (I suppose you're using the word line to mean a series of moves.)
I also suppose you're using "theme" to mean knowledge that can be generalized to many positions.
In this case my answer is lines only make sense in the context of themes. So to get better, first you have to increase your overall understanding. I guess you might say "learning more effective themes." You can memorize moves in hopes they'll make more sense in the future, but that's not a good way to go about it.
Hi
Have been playing chess for a while and am looking to improve.
Watching the US champs this year you see the lines developed by super strong players through analysis and study. Us mere mortals (well me at least!) tend to see themes in games rather than explicit lines. Eg a pawn led game or a knight ending, a stuffy middle game. My reference point would be a similar game that I have played and I would use similar tactics rather than a particular line to arrive at a favourable position.
So my question is what is the best route to improvement other than playing more chess and seeing more of these positions (which I will do anyway) is it ok to continue playing themes or does real progress only occur through deep study and development of lines?
I hope the above makes sense to someone (anyone!) and starts a discussion.
Peter