I feel like the people who are most passionate about this issue are the ones that were most active in posting (quality content, not Facebook tier memes), and they're the ones most likely to move. Reddit can survive on a casual audience, but if the 'experts' ditch reddit, the content quality is going to nosedive further than it ever has, until it's basically TikTok with links.
I've seen a lot of talk of people nuking their accounts, which is both the best and worst thing they can do. Quality posts / comments disappear, and there's no one around to replace them. Lack of said knowledge then makes people look elsewhere, be that here or the other next big thing, whatever that may be. Yeah, yeah, everything's probably archived somewhere, but the days of 'search term site:reddit.com' may be going away, and I'm sure that drives a decent amount of traffic.
Edit to add: It's damn hot here, and I've basically talked around the point I was trying to make; I think reddit leadership is making stupid ass decisions, but I don't think they're stupid enough to call anyone they're driving away freeloaders. The site would be nothing without the people that contributed quality content for years, and these moves are only driving those people away, in turn killing the volume of new quality content. They may make money short term, but I can't personally see the site going another 18 years, not without it being a total husk of it's former self.