I see reddit less as a website and more as a collection of communities. Each community has its own set of reasons for hosting itself on reddit vs other locations. Therefore I would predict that in the absence of reddit, not every community would move to the same place.
I also noticed that in recent years many subreddits have increasingly been taken over by memes and other low quality posts and so users looking for more substantial content have already moved elsewhere.
But some others have still been the best places to get early information on certain topics. For example /r/stablediffusion had a lot of people posting their novel uses and techniques for image generation. The QR code topic which is now blowing up here was already being talked about on reddit a week ago.
I also noticed that in recent years many subreddits have increasingly been taken over by memes and other low quality posts and so users looking for more substantial content have already moved elsewhere.
But some others have still been the best places to get early information on certain topics. For example /r/stablediffusion had a lot of people posting their novel uses and techniques for image generation. The QR code topic which is now blowing up here was already being talked about on reddit a week ago.