Can you elaborate on why you think reddit is pushing out the weirdness? I don't think it's a zero sum game, you can have both normies and weirdos in entirely separate subreddits.
And what does the existence of such a place at all mean to a prospective advertiser? Imagine a viral picture of your ad next to one of those posts.
But okay, let's ignore porn. How about subreddits that deal with subjects like depression, gender issues, politics, etc? What do you sell to those? Maybe a book or two but probably not very much. And they're also ripe for "hilarious" ad/content mismatches.
It seems to me that from the advertising point of view, Reddit would be a lot more desirable to advertise on if it was nothing but endless cute cat pictures.
Surely there should be marketers that see "Imagine a viral picture of your ad next to one of those posts." and realize that everything apart from "Imagine a viral picture of your ad" is often irrelevant.