That's kind of all that Reddit is to me. There are some exceptions, but for the most part Reddit posters are some of the stupidest humans on the internet.
They are great fun with cat pictures and other stupid content. And you'll have the occasional laser-focused sub-reddit (that will be a loss).
The occasional laser-focused subreddit has been my bread and butter on reddit for the past 15 years.
I never access /r/popular or /r/all or any of the default subreddits, all my usage on reddit is from niche communities about my hobbies, and through the past 15 years each new hobby I started there was a subreddit to kickstart it full of information and a community. That's going to be the biggest loss.
Most of reddit the past 10 years has been shifting towards new users just lazily scrolling /r/popular but those users are not profitable, they don't generate value, the ads will be poorly targeted. The laser-focused subreddits is where the value of reddit as a platform comes from, I don't like advertising but I could tolerate targeting on those subreddits as it'd be relevant without invading users' privacy (like the old days of AdSense using the context of the page for ads, not profiling the user).
The vast majority is utter stupidity, I agree, but that is a part of reddit that you can completely avoid if you are a bit more of a power user... It will suck when it dies.
Like my username says, I'm definitely not anything close to a power user, but you're 100% right. Moving to a new city, need info on your current city, or just visiting somewhere? Check their reddit out, between searches, maybe the wiki, and asking questions, you're set. Got a question on random topics? Find the 3-4 subreddits and fire away, no need to worry about quora or stupid articles online. Worst case the community you ask will have some RTFM-attitude to them, but boom - now you got a manual. And like you said, new hobby? Bruh, hit the wiki & the sidebar, go through their resources, ask the community for more if you feel like it. Get detailed help for your issues inside a week, for sure. It's ridiculous how useful it is to have a curated list of resources and a community ready to talk you through those resources, on day 1 of your future hobby, for free. For pretty much all interests. Shit was glorious.
I've read about some people calling for a return to forums. That lacks the one-stop-shop-for-all-interests feel, though - besides, subreddits are quick to tell you about other online communities you should hit up. For some of the older folks on here, how were the old newsgroups compared to reddit? From the little I know - and I mean "I learned about newsgroups from a joke on the Simpsons" little - it kind of sounds like Reddit...
They are great fun with cat pictures and other stupid content. And you'll have the occasional laser-focused sub-reddit (that will be a loss).
But the vast vast vast majority? Utter stupidity.