To be honest it is to be expected, people will flock to the most active (and consequentially better maintained, at least subjectively) instances.
This might only change once these big instance become saturated and close signups, though even still I expect to see only a handful of Lemmy / KBin instances staying relevant once the dust is settled, especially with the recent precedents like Beehaw defederating from “too open” instances.
Talking about Reddit is like thinking about your ex right after the break up. It sucks and oddly satisfying at the same time, and it will pass 😅