Migrating communities from one platform to another is a lot more complicated than most people assume.

Cold start problem: initially the new community has no content archive and only a few users, most people are lazy, it takes time to relearn the ui and set up subscriptions(there is no good way to export/import subscriptions and saved posts)

Transfer of moderation: some people are going to take the opportunity to seize ownership of the new community, and the community will split up

Discoverability: reddit gets a lot of user traffic from google since google search quality has gone down and people add site:reddit.com to their search

We need a new form of social media where users and communities can easily export their content and data. A reddit clone with a similar UI is not enough.