"Loyalty = who spends the most. No? "

NO!

I think you confuse the purpose of loyalty programs with loyalty.

A person who buys J class all the time, gets many of the benefits (concierge, bigger seat, lounge access, priority board etc.) and doesn't need status to get them. Loyalty there must be encouraged through better product not status. They can take their business elsewhere and don't worry about status too much (I know there are always exceptions). Status doesn't matter-product does.

A person who buys Flex all the time and won't get those benefits unless they can achieve status. These persons are motivated to spend marginally more than they would normally spend or at least spend with one airline/alliance more than they would otherwise since they receive real or perceived benefits for doing so. This person can also take their business elsewhere but may be reluctant to do so if the value proposition is there. Status matters and both the pax and the airline benefit.

A large purpose of loyalty programs is to get those people in the second or similar scenarios continuing to buy into their system and hence more revenue for the airline. The individual annual spend may be the same or less than the person who buys J all the time but their motivations are quite different.

I am not opposed to spend as a criteria or as a way of determining status but to say $$$ = loyalty is not correct. It is much more complicated and the above scenarios are just a couple of ways of looking at it. Each of us has a unique reason why we want status (or don't care)--the airlines have to figure out a way to get more of us in their doors without breaking their bank. True bottomfeeders are likely rare and don't make a big difference positive or negative to the airlines. High spenders are also likely rare and could make a difference but may not be at all motivated by loyalty programs. The big question is how much of the status-seeking middle spenders can an airline capture with its status/loyalty program. Will be interesting to see how these spend/hybrid spend/BIS miles approaches play out for loyalty. I don't really think any of us know the answer but obviously some airlines feel they are giving away too much with just BIS mile-based programs.