Best news in the world for SEOs. Worst news in the world for people searching on Google for solutions to obscure technology issues or looking for coupon codes.
I find this comment quite insightful actually. Everyone is focusing on "can reddit get users without Google" and forgetting the other side which is "can reddit be searched without Google?".
It amazes me that reddit has maintained such a terribe search service for so long. It has been consistently and impressively bad. The most basic filtered full-text search would be better. But then again, if google is going to do the job for them, why waste your time and resources on improving search. Maybe if they blocked google, it'll force them to improve reddit search.
Reddit's on-site search is so incredibly awful. It's impossible to find anything even remotely like what you're looking for. If they de-index or go behind a paywall or something, it will become useless.