Completely agree with 53rd way
I think there are things you can do to help or hinder, but you're working with what you have. So good routines, dark nights, light days, consistent nap timings etc are all helpful. Things like running to every whimper and giving in when they get out of bed for the fiftieth time are unhelpful.
But... I think a lot of sleep is developmental. Ds was about the worst sleeper of anyone I know and looking back, I don't think we did anything 'wrong.' We were given a lot of advice by medical professionals and 99% of it we were already doing. The sleep specialist at the hospital told us we were doing everything right and that a small proportion of kids just take a very long time to get it. That, frankly, was the best bit of advice we ever got.
Ds did get it, eventually, at 18m. It was absolutely nothing we did or changed, he just grew into it. Literally over a week he slept through from waking screaming 6-10 x a night.
With regards to cc - I think it can work if the child is waking from habit. We tried it with ds and it made things very much worse. Looking back it was a daft thing to do for him because his problem wasnt habit it was separation anxiety.
So I think that kids are all individuals, and there's no one size fits all approach. Cc can work, but it's not the panacea for all ills.
You can certainly help or hinder with habits and routines. You can nudge. But I don't think you can do any one thing that will guarantee sleep.