What happened in Tuam and other places is bad enough without saying the babies were 'dumped' by the nuns - I think even Catherine Corless has objected to that word.
We know there were 796, we know each of their names, because each baby was named, baptised, their birth registered, and their tragic death, the date it took place and the cause of death were also officially registered - how do you think CC was able to find out so much about the babies? Because it was all in official records.
Over the space of several decades, disused underground spaces dating from Victorian times were used as a communal grave to inter them. The area has a number of old communal graves, from the old Workhouse, later military barracks, the convent, etc. They weren't properly marked and some of them were built over in the 20th century.
We know who the babies were, we know the area where they were interred, but we don't know where exactly each one was buried as there were no grave markers. The Memorial Garden built over the graves commemorated each and all of the tragic little lives.
So not exactly 'dumping'. What happened to women and children in Ireland in the past is grim enough, the infant mortality rates were bad enough, society's abandoning of unmarried mothers and excusing of unmarried fathers was bad enough, the inadequacy of social care in early independent Ireland was bad enough, the outsourcing of care to the church without adequate resourcing or oversight was bad enough - the historical facts are bad enough.