Enshittification refers to a process with specific phases that ensure services will degrade at the expense of users, and then business customers, so that shareholders can extract as much profit as possible from both of those groups. It was coined by Cory Doctorow, who explains it here:

Here is how platforms die: First, they are good to their users; then they abuse their users to make things better for their business customers; finally, they abuse those business customers to claw back all the value for themselves. Then, they die.

I call this enshittification, and it is a seemingly inevitable consequence arising from the combination of the ease of changing how a platform allocates value, combined with the nature of a "two-sided market," where a platform sits between buyers and sellers, hold each hostage to the other, raking off an ever-larger share of the value that passes between them.