Just noticed that yesterday. Almost made me give up on logging in and posting. The day old reddit is gone will probably be the day I can't tolerate it any longer.
I already avoid Reddit search results in Google because the site is crap, unless there's no other option (and then I force it to Old Reddit), just like I avoid the sites full of popup ads.
Without users writing new content (because the site is crap) the Google stream will dry up too.
Bots will generate content on Reddit using LLMs for years to come. It will be an uncanny valley full of apparent UGC and interactions. People who still use search will be pointed there and say, see, you don't need to use these new-fangled chatbots! But they'll be looking at pre-generated chatbot output. The bots will get stuck in a reinforcement loop where reddit content generated by bots is used to train the LLMs for the next generation of bot, and "reddit recommendations" will devolve in old wives' tales, stuck in the past, the echo of the voice of a generation long gone, repeated by mindless zombies.