Often we can forget what self-soothing looks like, instead thinking it only reflects calming behaviours. However, we all respond to anxiety differently and not all self-soothing is actually beneficial.
The premise behind extinction sleep training is that infants (and toddlers) are being taught to "self-soothe"; however, this ignores key points of what self-soothing abilities can be expected from children and how distressed they are at the time of separation. Instead of focusing on these extinction methods, gentler methods that respect where the child is developmentally should be considered.
We do a lot to try and ensure our children are empathic. And yet, there is one thing I see happen with alarming regularity in our young toddlers that sabotages so much of what we are aiming for.