Reddit's always been a bit of a weird site in this regard. Most sites closed off a long time ago and put so many ads everywhere. Old Reddit is still alive 5 years after the redesign and it's been so easy to avoid ads on Reddit in general. While most places have aggressively pursued monetization, Reddit has been a place where you could avoid most of that.

Even the way that Old Reddit showed ads was so quaint. If you look at Old Reddit without an ad blocker, you'll see an ad in the list of 25 items, but it has a different background color so you can easily visually differentiate it from the real content along with two high-contrast things noting that it's an ad. Sites like Twitter and Facebook have been minimizing your ability to differentiate ads from content by making them look nearly identical with a tiny, low-contrast marking that they're ads. Of course, New Reddit shows ads with the same tiny, low-contrast marking that other companies use. But unlike others, Reddit still allows you to choose the Old Reddit experience.

Yes, in some ways the writing has always been on the wall. In other ways, Reddit has been a bit different. They've largely ignored the kinds of things that other sites have gone after. Yes, when you've hitched your wagon to a company's site, you're at a certain amount of risk. That's also true of users who might find the site infested with ads or changing how they're allowed to do things. At the same time, Reddit has resisted that direction for so long that most people assumed it would continue. Why now? Why not 5 years ago?

It seems like the thing people are reacting to is the culture shock. Instagram was never open. They wouldn't even let companies schedule posts for a long time. Facebook was barely open, but never had the kind of ecosystem that Reddit had (and often fought against third party access). Reddit's policies felt really different and they aren't changing in a gradual fashion. It's not like Reddit told Apollo, "we're going to start charging 20 cents per month per user" and Apollo only works for those paying $1.50/mo for Apollo Ultra (and then a year later Reddit wants 50 cents and then a dollar and slowly Apollo Ultra goes up in price and more people move away from it). It's not like Reddit put in limits like "you only get 100 API calls per day per user" which would be 30% of an average Apollo users' usage. That would start bleeding users from Apollo over time, but not feel like slamming the door shut - and maybe Reddit charges $1/mo for unlimited API calls for the user and only those paying a subscription fee can get the unlimited calls. That would offer a way forward that users might grumble about, but could work with. Free users could still get a decent amount of usage and people who really cared could subscribe to a new Apollo Ultra at $2/mo. In fact, it could drive sales of Apollo Ultra - maybe 5-10x more people start paying for Apollo Ultra.

I think the big shock is that Reddit went from so open to so closed in one step while Reddit had historically accommodated the community's resistance to monetization. Old Reddit has stuck around for half a decade now. Despite being one of the most visited websites, a lot of monetization opportunities seemed to be ignored. Condé Nast/Advanced Publications seemed to mostly ignore the site. It was spun-out with Advanced Publications remaining owner and just kinda went along. Even after raising $200M in 2017, Advanced Publications was still the majority owner (and I think they're still today even after Reddit raised another billion dollars).

Lots of younger sites/networks have gone public with a lot less traffic and aggressively moved to monetize. I'm not saying this was the case, but it always seemed to users that Reddit's owners were a bit disinterested in its potential monetization and were mostly fine ignoring it - allowing users to easily block ads, keeping Old Reddit around, allowing free access for ad-less third-party apps, etc. In that environment, it does come as a shock. Reddit felt like this hidden place (that also everyone knew about). It just felt different.

You're not wrong that building on someone else's site is risky. At the same time, I can see the shock from such a sudden change to a site whose reputation was quite different.