Seems an odd decision from Aldi but it's up to Aldi how to organise its tills, who to put on them (over 18s, under 18s who need someone else to do alcohol sales, those who object to handling certain items on religious grounds) and indeed how many tills to have open. It's up to customers to decide whether the level of service is acceptable. I assume it's part of some diversity policy here where they want to attract a more diverse workforce, or maybe there are recruitment difficulties, so they take who they can, but it seemds to me it makes life marginally more difficult for management other staff and customers.
But why peopel go to the press about it I don't know, especially if it is clearly signposted that only certain tills can handle alcohol sales.
People look for something to complain about or look to take offence over some minor issues and perhaps don't have any important issues to worry about.