From Wikipedia:

Enshittification, also known as platform decay,[1] is a way to describe the pattern of decreasing quality of online platforms that act as two-sided markets.

From the guy who coined the term itself:

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.