The purpose of an API is the agreement, more than the access. You can always reverse engineer something, but your users won't be too happy when things randomly stop working, whenever reddit chooses.
This is not a useful comparison. A failure of an ad blocker means you don't see an ad while using the service. Big deal. A failure of a reverse engineered glorified web scraper is that the app stops working, completely, for all users of the client, at once, until someone fixes it.
Yes, it could be democratized, but most users wouldn't understand any of this, and say "ugh, this app never works". It would be a user experience that reddit could make as terrible as they wanted.
What I'm talking about already exists by the way. Stuff like nitter, teddit, youtube downloaders. I once wrote one for my school's shitty website.
Honestly I don't really care about "most users". To me they're only relevant as entries in the anonymity set. As long as we have access to such powerful software, I'm happy. I'm not out to save everyone.
I understand what you're saying, but I think this is the key to my point:
> It would be a user experience that reddit could make as terrible as they wanted.
It's an unfair cat and mouse game. Yes, effort could be made to fix it each time, but, if reddit chose, they could force everyone into the "most users" group, when the only app works for 5 minutes a day, and people get bored, because they decided to randomize page elements.