They're different kinds of experiences.
Forum-type things like Slashdot, Reddit, Hacker news, Reddit, etc. put the focus on the topic or community.
Micro-blog type things like Twitter, Mastodon put the focus on individuals.
If you want to see what your favourite author is posting about, or what your favourite musician is working on, or maybe behind the scenes pictures from a sporting event, microblogging platforms are great for that. Journalists also loved them because they could follow specific other journalists or other key people in the area they cared about, and get direct info from that source.
OTOH, if what you care about is a certain topic (F1 racing, beebop jazz, etc.) then forum-style platforms are better because the focus is the topic rather than the individuals.