My experience with Reddit agrees with everything you said. It's true that niche subreddits had very few posts through the day, but at least they hadn't overcrowded comments with nothing substantial to say. And engagement was easier, despite being Reddit and its karma fuckery.
It wasn't the same, for example, posting a meme on r/memes, with millions of users, or posting a meme on r/adhdmemes, with almost one hundred thousand users. And user mindset was also very different between them.