I agree that people for whom this "method" has "worked" a) have selective memories - I think they blank out how bad it is and b) present their stories verrry misleadingly sometimes (i.e. they LIE).
One anecdote will perhaps suffice. I love this one because it really shows that you canNOT take people at their word when it comes to something that (ridiculously) is as highly-charged as infant sleep.
My cousin has a 5-yo ds. She had always
bragged about what a fantastic sleeper he was. Slept 6 hours a night straight away (like, when she brought him home from the hospital!). ETc etc etc. I asked her, after I had my dd (her ds was about 3 at the time), did she ever sleep train him, or did he go through any periods where he didn't sleep well? My experience with dd was just so completely different from what she had reported that I was sure she must be leaving something out. She VEHEMENTLY denied it and insisted that he NEVER, and I repeat NEVER, had any issues sleeping through the night, and that she NEVER sleep trained him.
So - fast forward almost 2 years and she is finally far enough away from the baby days to be honest, I guess. I was complaining about dd's sleep issues and said "wow, I guess your ds is just that rare super sleeper." She said, "oh well, sometimes he didn't want to go to sleep, so I'd just put him in his crib and say night-night and put in my earplugs. Sometimes he'd scream 45 minutes or so, but he always ended up going to sleep."
!!?!?! Far cry from what she had said before.
And now I know a ton of people with small kids and most of them have gone through short or long periods of major sleep disturbances, with very rare exceptions. Little kids just do not sleep the way adults do and there are bound to be some hard times in most cases, IMO. Being the perfect AP parent certainly will not insulate you from having kids that wake all the time, but I do not think being a "CIO parent" does either.
Most people I know are not doing CIO, but a few moms I've met have talked about doing it. Every. Single. One who have talked about it with any candor have admitted that you have to do it over and over again.
Which makes sense. It's not logical that after only a few nights, all nighttime needs are so completely extinguished that the child will never have to cry again.
I went through several really, really rough patches with sleep issues. I know how the OP is feeling, for sure. But it feels SO GOOD to get through it, to be on the other side (dd at 2.5 yo is not a perfect sleeper but wayyy better than before) and know that I never let my child scream by herself in her crib - that DH and I have always been there for her and WILL always be there for her at night, as long as she needs us. It's a GREAT feeling.
Hang in there.