I don’t think leaving them alone in a bedroom to fall asleep is considered “neglect”. As long as their needs are being met during the day and they otherwise feel loved.

I say to let the baby cry it out. Make sure it’s been fed, diapers been changed, it’s in a warm safe bed, etc. Life is much better when they get into a sleep routine.

If the baby’s crying still after an hour, check it’s diaper, lay it back down, and stick with it.

I’m SO glad we are out of that stage of life. It’s been about three years. We established good sleep routines early and my children all go to sleep and nap when they should without much complaint.