The thing with online slots is the effect of a lower RTP is cumulative, an increase in the house edge from 4% to 6% is a huge difference in the long run, and whilst individual sessions will swing widely, as slots are so volatile, the overall long term effect is still that the house has increased its edge by 50%.
You can get away with low RTPs on compensated machines with small jackpots, not least because a compensated machine will always actively 'aim for' its target percentage, often kicking back a portion of a player's losses back to them and giving them an obvious stop point. You can't compare compensated UK AWPs (which even now have a maximum prize of 100x stake, and back in the day were as low as 24/30x stake) and their RTPs, with online slots that are (a) Random and (b) Have top prizes often measured in many thousands of times stake.
