Youtube could pivot to nothing but cat videos tomorrow and they would be perfectly in the right to do so.
But these companies are a lot less respectable than YouTube has been to date, and people know what they are getting.
The issue here is YouTube's standards are changing and that deserves to be discussed. And condemned, it is change for the worse (even if in some sense it is probably inevitable).
It's also within people's rights to criticize them for it.
They have a fiduciary duty to their shareholders.