You mean just having a standard price for everyone that goes into a supermarket and wants to buy groceries? Sounds awful.
As I said, "members only" prices have been a thing since forever
If you think that overall these new prices aren't making more profit for the supermarket then you are very naive.
And if you think preventing them from doing so would result in prices dropping, then you are very naïve, they would simply raise prices to offset the losses caused by their inability to harvest that data
Exactly what I am doing

But I have the transport and time to do so. Many people will not, and will be forced into this data harvesting.
Again, nobody is being forced to do so, they could just not participate in the loyalty scheme, and instead pay the higher prices - or are you suggesting that shopping at M&S is cheaper than paying the "standard" prices at places like Sainsbury's, Morrison's, Tesco, Asda, etc.?
At present we have the situation where people can pay less for certain items, in exchange for letting the supermarket track their shopping habits. Whilst not ideal, is this not the lesser of 2 evils when compared to them simply not being able to afford those items at all?
Lovely Monday morning email stating our council tax has gone up 5%
7.5% here, and we've not had a recycling collection in over a month
Honestly, I don't even mind the increase, in absolute terms it's a trivial amount (~£10/month), it's more the fact that we keep paying more every year, and get less back for it. I'd rather they put it up by a decent amount and in return we actually get reliable bin collections, roads that have fewer craters than the surface of mars, more police, youth services to keep the bored teenagers entertained rather than getting up to mischief because they have nothing better to do, etc.