I reckon that's because Google largely works on pull models: you ask for something and G gives it to you. Its services superficially appear like databases just sitting there, even if we know that's not the case.
FB and Twitter, on the other hand, largely work on push models: you log on and the app will give you stuff to look at, as well as notifying you incessantly. It easier to perceive the app's own agency and priorities.
In this sense, it explains why Google tends to get heat over Youtube: because it's closer to a push model, both with homepage and suggestions.
Also, Google services are largely useful to get stuff done, in a way FB and Twitter are not. That gives G a big pass.
There is an interesting speech by Zeynap Tufekci on this topic:
However you frame it, Google are showing you things you want to see - it's an affirmative feed back mechanism.
Facebook at best do that. Frequently they show you things you don't care about. Also things you don't want. It's an adversarial feedback mechanism.
In this light it's not surprising Facebook has earned a lot more ire a lot more quickly - though not undeservedly either.
On some level this still feels like you can squarely pin it on "optimizing for engagement". I highly doubt Facebook would be earning the anger it currently does if The Feed has remained a simple linear timeline. They were functionally getting into editorializing when they went with the new thing.
We're basically there already as far SEO spam goes, and Google goes to some efforts to try and minimize that because it's a bad search experience and drives people away.
Kind of gives perspective to how long Google (with Android, YouTube, Groups, GMail, GSuite, GCP) has managed to go relatively untarnished (as a brand) but Facebook couldn't.