>Large communities can't meaningfully migrate off it.
Yes they can, Digg migrated to reddit, Facebook migrated to Instagram. If Reddit becomes insufferable for most of their users to use they will migrate. Never forget the internet 1% rule [1], just the right set of users have to migrate to kill the site.
it's not enough to be marginally better. you need to be a LOT better to overcome network effects and activation energy.
reddit became substantially better when digg ruined their product. actually, digg didn't work at all when they rolled out their new version, so it was (approximately) infinitely better.
Yes they can, Digg migrated to reddit, Facebook migrated to Instagram. If Reddit becomes insufferable for most of their users to use they will migrate. Never forget the internet 1% rule [1], just the right set of users have to migrate to kill the site.
[1] https://en.wikipedia.org/wiki/1%25_rule