Here’s what I can advise… I used to be in kind of the same spot that you are, and I think the reason why is partially because I relied on tab and set arrangements to learn a song. For instance, if someone had asked me to play a song I didn’t know, my first thought would have been “I need a tab!” Tab is really a great tool, but if we aren’t careful, we can end up in the habit of needing to be spoon-fed set solos, etc. So for learning new songs, my plan of attack was to memorize a set solo from a tab or lesson so that I’d be ready whenever I needed to play it. But that’s really not the best way to progress as a banjo player overall, because a great banjo player doesn’t just have solos memorized for all 1,000 songs that they might need to play someday; they have a method for playing the songs on the fly. I saw a video once of guitarist Bryan Sutton playing a song. He said, “I’ve never heard this song before, but I’ll try it” or something to that effect, and when it came time for his solo, it sounded like he’d played it a thousand times. Do you know why? Because he probably had played it a thousand times by playing similar songs. All he had to do is put the pieces together.
Here’s an interesting analogy. Think of playing a solo like solving a puzzle. I personally love speedsolving the Rubik’s cube; and there are over 43 quintillion possible combinations that the pieces could be in. If you were to start with a solved cube and then used a preset scramble, you could just reverse the moves you used to scramble the puzzle, practice it a lot, and then volia, you could impress people by doing it quickly! But what if you wanted to solve the cube quickly and consistently with any scramble thrown at you? If you used the method above, you would have to memorize over 43 quintilllion sequences!! But the way speedsolvers solve the cube is by using a combination of intuition to get the puzzle into a state that is plausible to solve using prememorized sequences of moves (algorithms), and use those algorithms to solve the rest. These two things- intuition and memorized algorithms- are what make up an on-the-fly solve.
It’s the same with playing a banjo break. The psuedo-speedsolve is a set arrangement from tab, etc. So when this scramble, which is a song, comes up you can just use your memorized solve (A.K.A. solo).
But for solving a new scramble (playing a new song) on the fly, banjo players use both intuition (improvisational licks that carry the melody) and prememorized algorithms (licks that fit over a chord).
So when you practice, don’t just play songs over and over. Instead, play, listen, and examine the songs and ask…
- How can I apply the principles taught in this arrangement to an improvised break?
- What did the arrangement writer (Ben) have in mind to show me when he wrote the arrangement?
- If I cannot play the arrangement easily after much practice, why not? What could I change about this arrangement that will more easily suit my playing style?
- What exactly (name it) is preventing me from being a better banjo player right now?
When you can’t play an arrangement easily, don’t just play it over and over with a bunch of pauses thinking, “I’m a bad banjo player because I can’t play this arrangement” hoping that maybe if you play it a thousand times, you will transform into an amazing banjo player. Focus on EXACTLY what is stopping you and work on that specifically.
Learn the basics of writing your own breaks (the Make-a-Break lesson is a great place to start) and work on that principle, viewing tabs and set arrangements not as end-all be-all guides, but rather examples designed to teach principles. The goal is not to be able to play every solo on the lesson page perfectly, but rather to understand how these solos work intuitively, and apply those principles to your own arrangements.
Learn the basics of backup, and play basic backup behind slower songs. Once you have your foundation rock-solid, start to play it behind slightly faster songs. Then, add some intermediate techniques and practice them behind slower songs, then faster songs. Finally, do the same kind of thing with more advanced techniques until you can play advanced backup behind fast songs.
All this will not come super quickly. Make sure that you have the foundational techniques and principles ingrained in you, and move on only when you know those things very well. It’s better overall for your progression to know and understand the foundation extremely well than to kinda-sorta know a bunch of advanced stuff.
And, sorry for writing so much and if I seemed negative… This is what I personally have learned over my banjo playing journey, and everyone’s brains are different. I hope this long post helps you; I love to write, and sometimes I just don’t know when to stop! 
Let me reassure you that what your going through is quite normal. You study and practice for hours and see little or no progress for your efforts. But one day you’ll pick up the banjo and your fingers will pick the right strings and fret all the right notes. I know from personal experience because I have trodden that same path.
