The examples given are all British flights, with presumably large numbers of non EU citizens. Is it working fine for other flights? Do passengers just need more time for customs if flying to a non eu destination? This reeks of Brexit consequences to me, rather than era problems, which probably don’t help.

People in charge of airports, who have known about this for years and did nothing, claim that not preparing for these changes has left them entirely unprepared.

This law stems from 2017. Some airports have just put down a hundred terminals to do this, some placed a dozen. Guess where the trouble will be?