True, and having the benefit of hindsight, it’s easy for us to judge.
The trouble is, Apple’s feedback process is so opaque that we can never know the details. All we have is the feeling of “a simple test of macOS with a third party firewall before unleashing it to the world would have shown the problem”.
For a piece of software on which countless people rely upon (which macOS and iOS are), the “beta” begins after exhausting all internal means of detecting regressions and unwanted behaviour. It’s not cheap but they can’t just dump something and expect unpaid, third party developers to report all the bugs (while never getting a reply on that feedback app).