I got in on reddit super early. Every few weeks I get a message from someone referencing a comment a decade old, now either featured in some youtube video or coming up in their google search. It's unnerving shit and I check my politics there a lot more than I do here. Just as a matter of user safety it's good that our posts disappear after a month or whatever. Maybe it's eventually a few months or a year, but if we ever return to the normal model of forums preserving everything forever it's a big infosec risk.
The internet is the sole means by which I got information and turned leftist. The means by which I got involved with local groups, :vote: d slightly better, went to protests, argued for fair pay in my workplaces, made more effort to stand up for people who get fucked over, and came to convince a couple meat-space friends to genuinely support communism. My turning point was hearing how it's all great, learning how easily I could get the commie manifesto for a quick read, I read it and went "well shit that seems all kinds of reasonable" and that did it for me.
Anecdotal evidence, I'm but one person, but online spaces with genuine talk and information helped teach me how to make the world better, I fail to see why that wouldn't be the case for many more people.