Developers are pissed off at Twitter for two main reasons:
1) Developers helped build Twitter as it exists today. With their hard work, sleepless nights and toil, they created the ecosystem that allowed Twitter to grow into the giant they are today. Now that Twitter is big, they are saying thank you by more or less shutting down their API for any serious Twitter integrations.
2) Twitter said, "we'll work with you" regarding API limits, but they didn't mean it. People that built things in good faith are now realizing that Twitter didn't act as such. If you put a lot of effort into building an app that utilizes Twitter's API, you'd be rightly pissed about this too.
I agree that it may have taken a long time for "the obvious" to set in with regards to Twitter not caring about their 3rd party developer ecosystem. Hopefully, as the OP points out, its pretty obvious you'd be a fool to build anything on Twitter anymore.