I usually don't comment on these types of threads, because it can be a controversial topic and I don't like heated debates to get started. But I thought I'll be brave and share my story. Well for my LO's first 2 months, it was hell getting her to sleep. Nighttime came and it was horrendous. It would be 4 hours at least of her screaming while I was doing everything I could to soothe her. Everyone had a suggestion of what I needed to try, but I tried all of them. My LO hated swaddling and the sling. She didn't like her swing or vibrating chair. She wouldn't take a pacifier or nurse to sleep. White noise things and light shows didn't work. I could go on and on but I would try everything. She was full, dry diapered, and burped. Trying to soothe her by carrying her or rocking her for hours and hours were making me cry every night. Seeing her screaming was heartbreaking, and I was going insane.I'd feed her and feed her but even that didn't work.
Well one night I fed her good, and cuddled her until she started her usual screaming. I told her I loved her and placed her in her crib and stroked her head. I stood outside her bedroom door in tears myself praying this night would be better for her. I just sat there peeking at her from the door, heartbroken and listening to her cry while feeling like I was a shit mother. She cried for an agonizing 43 minutes before she went down. 43 minutes as opposed to 4+ hours when I tried to do it.
The next 2 nights I put her down for bed, and it was 20 minutes of crying. Days 4-7 it was 10 minutes. A week after I tried letting her cry in her crib, she never cried again at night. Since then, out routine is bath, feed and then put her in bed. She happily babbles to herself now for about 30 minutes and then drifts off. She now knows how to soothe herself to sleep for naps 3x per day also, and falls asleep 3-5 minutes after I put her in her crib during the day, no crying at all.
I know most people on BNB are very anti CIO, and would never do what I did, but I am glad I did it that week, because it has improved my LO's bedtime. Most people who do CIO, are doing it as a last resort, as you said. Moms who let they babies CIO are usually absolutely heartbroken that they need to try this, and they get snubbed like they are shit moms. I hate when people use the term "neglect" and "abuse" to decribe moms who use CIO.
That being said, I just wanted to say please only do what you feel is right for you and your LO. Don't feel pressured to try CIO and also don't be pressured to not try it if you feel you want to. I hope you have better luck putting your LO down to sleep.