Free speech is a civil right, as civil rights have grown in the US it has been extended to those that civil rights have grown to encompass. It's not just the privileged few (or even the privileged majority) that are angry about a loss of this social more.
> but now there are decentralized public means to criticize the powerful.
What you are calling "the powerful" seems to me to mostly be average normal people who just happen to not agree with the current sentiment in vogue. Most of the people who've found themselves on the wrong end of the consequences meted out for attempting to exercise freedom of speech would hardly qualify as "powerful" under any lay definition.
The public square is supposed to belong to everyone, and freedom of speech is the social more that ensures this is the case. We've lost or are beginning to lose this social more, and doing so has disastrous long-term and far-reaching consequences for our society.