To add to this. My dog is one next week. When he was a puppy I used a sling too, he was tiny (he’s a mini dachshund) but it was easier to throw him in a sling and keep my hands free. He was too young g to be on the floor and it was a perfect way of socialising him. He went everywhere with me that was allowed, I think we spent about a month trailing pubs, shopping centres , stations etc with him.
The result is a little dog I can now take anywhere because he is so well socialised.
I have a much bigger issue with people that have dogs, don’t socialise or take them out often and then suddenly pop up in crowded places with an animal that’s doing cartwheels on the end of a lead barking and snarling at anyone and anything. At least the dog in the sling or the pram is out and getting a bit of mental stimulation.
And yes, I will end this by confessing he does have a birthday cake for next week because he iis part of the family