This may well be, but in the old days there were no subreddits. Five years ago, I didn't have to go scrounging for the good content. So, subjectively the content available through my default settings has gotten worse.
I remember the day I learned that some of my new co-workers were really into Reddit. It was strange because I remember thinking how superficial their lunch-time conversations were compared to what I'd been used to debating online. It was an "aha" moment. Here comes everybody.
Walked to school uphill, both ways, in the snow and with bare feet too, did ya?
Reddit is, and has always been, a large organic community that has always undergone change. Reddit had to introduce subreddits as a way of breaking up and categorising communities as things outgrew the "everything on the front page" model.
Getting big changes things, and I don't see how comments like yours are insightful when all the things you listed (yes, even the deep and meaningful posts and debates) are still happening on the site, your just need to sort through the noise.
Things like subreddits help you do that and get what's relevant to your interests.
I remember the day I learned that some of my new co-workers were really into Reddit. It was strange because I remember thinking how superficial their lunch-time conversations were compared to what I'd been used to debating online. It was an "aha" moment. Here comes everybody.