Or do I just need to practice it 50 million times until I get it
I may not say it as trollbuster frankly put it, but let me just say , if you are really at the level you are at to merit being able to study and practice (and say 'learned' ) certain advanced repertoire pieces, then you should certainly be able to analyze and figure out on your own (Yes, a teacher can provide proper guidance, but not hand-holding -> this only applies to beginners and less experienced music students) what is preventing you from increasing in speed.
You can play it a million times and yes, perhaps in 60 years you can play it blazingly, but even after a trillion times, the way you learned the piece will just be further engrained. Meaning, whatever corners you cut and whatever compromises you took to garner the speed through certain measure switches will just be more a permanent part of you.
I can quickly learn the arpeggio set of winterstorm etude and flub throgh it, just keep practicing it over and over again a few thousand times, and iwil be able to perfrom it at terrific speed, all w flubs and mush quality.
You have to dissect and get down to granular level each movement that causes you hindrance , analyze it, and work your technique through solving it. work that about a couple hundred times (that is all you need) slowly and then try increasing speed.
But this is basic advice known by all advanced students. Arent you that?