For me, it has a lot to do with fatigue.

When I started interacting with people on those kinds of forums, I tried to be genuinely helpful, like most of us.

When you see the same question asked over and over and over, when you see the same flame wars happening over and over and over, there are two paths in the long term. You either stop interacting on a regular basis and only react to interesting questions because you are tired of repeating the same arguments, or you gleefully dive in the cesspool and become a toxic bastard.

It’s especially hard to keep having a nuanced debate when the comments are flooded with people who are confidently wrong (eg recommending an advanced or niche distro, or even worse, Ubuntu to a beginner), extremely opinionated users (the anti-systemd or anti-Wayland crowd) and so on. You just end up being lost in a sea of comments and unheard. So why bother? Let the flame wars rage and move on.