I practice NF quite often. It doesnt give you the same kind of stamina that practicing longer songs does, but it does help if your reason for failing out is that your hands basically lose control due to the strain of playing above your skill level.
It wont make you much better at the sonhs, but it can help you not feel like you've destroyed your hands after attempting something a bit too hard.
I think what you really need to do is improve your technique and reading instead. Reading isn't black or white. There are degrees of skill in reading, and being unable to read a pattern fast enough to play it well is the single biggest problem most players face. Its hard to tell if reading is your problem without a lot of experience, bur generally ot ends up being the case.
Focus ypur practice on maps with similar patterns but slightly lower bpm to the 5* songs your trying to play.
Also focus on hitting the keys lightly. when.you press hard, and when you try to force your fingers to go faster than feels comfortable, you tense up the muscles that make your finger me upward at the same time you're trying to press the key, which slows ypu down and drains stamina. Pressing lightly results in faster finger speeds and less stamina loss.
To practice light presses, play stuff you can easily S and focus on pressing lightly. You will probably make a lot more mistakes by either not hittong at all, or pressing late, but if you can learn to press lightly on harder stuff after learning on easier stuff, it can make a huge difference.