If you have every switched from one curriculum to another (any subject any grade), can you please share about how the curriculum was different? (And also let us know what levels/ages you used each with)
My oldest is in 7th grade. Between my three school-aged kids, I have pretty much switched curriculum in every subject in every grade because what works for one doesn’t work for another. I would think most people have to switch more than they care to, but I don’t necessarily remember all the whens and whys. I do remember what I have used and why it did or didn’t work for a specific kid. You may get a better response if you tell us specific curriculum that you are asking about, or what you are using and why it isn’t working. 
The original question is very broad and, at least from my experience, would take a very long time to answer. If you will give some more details, I’m sure there are lots of people on the board that can offer you some valuable insights.