Trust your baby! Which you are doing. Some babies don't conform to book standard AP parenting, baby wearing, constantly being held plans. Yes, many babies DO, but yours simply may not. I've worked with babies who really do need to be put down and work out (not cry out, but work out) their stress and then just sleep.
You know your baby better than anyone. If she hates the sling, don't use it. My eldest one HATED any baby carrier, unless I was moving at a fast race walking pace. In those days they only made "regular" size slings, and I need a petite sling, or my babies roll into a ball at the bottom and scream. So, I just either held her or passed her off to someone else. Couldn't find a carrier to work. My other kids, I used OTSBHs or Tot Tenders (I don't think either of these are made any more) but not all babies conform to ONE way of parenting.
You got good advice, "Don't try to cure the fussiness, just tend to your baby." I learned that the hard way with my 2nd one and pretty much perfected it with my 3rd. I realized I didn't have to cure the fussies, I just had to hold and love the baby. I wish I had known that with my first.
Keep on keepin' on, Mama.