The Wall was replaced by an algorithm which sunk original content below a flood of ads, fake news, and externally shared content "you might like". We stopped seeing original content. Then, people stopped sharing personal stuff, as nobody interacted with it.
The need for growth. When facebook has roughly maxed out its user base, how does it proceed to grow? 1. Infiltrate comment sections on major websites and require commenters to log in via facebook. 2. Optimize facebook content to increase user engagement and keep their eyeballs moving across advertisements.
Facebook could have remained a simple and fun social network app for much longer, but the need for growth is destructive.
Things catch wind, and they try to leverage and survive long term .. changing their "core" value in the process, much to the despair of users. Twitter did change a lot too .. you could say the same for artists also.
I think in survival there's no real good measure of balance. If you don't overdo it, you're wasting "meals" and giving them to competitors. I don't condone it, but it seems a natural law of systems.