So far the people who were most likely to jump ship on reddit were those who were the most fed up with what reddit has become lately.
I just had my 10th cakeday on reddit about a month ago and I've seen a steep decline in quality for both posts and interactions for the last 4-5 years, with it accelerating in the last year or so. Those that never tried old reddit on desktop or a 3rd party app see no reason to jump ship for another platform, and a large portion of the rude commenters and trolls showed up after the new layout was default and reddit had their own official app in the app stores.
Reddit just filtered out most of the people that made the site what it was in the first place. If it was turning into a shithole before all the people that actually care about the site left, just imagine what it will be like in the coming weeks now that we're gone.