I'm just saying Ruby is good at enabling DWIM and Rails has taken it and run with it to the point of magical thinking.
It's very hard for an app developer to test for vulnerabilities such as this one which seem to involve a combination of contributory factors. When magical stuff is constantly willing to help the app developer out in the background, it's very difficult to get a handle on what our true attack surface is.
Rails has definitely started to get complex, which is why many have chosen to go towards the simplicity of Sinatra, Rack etc.. Any time a framework get's complex this happens.
Look at big data and AI. There are loads of permutations. How do you prevent stuff from just happening? How do you make sure that things are correct etc.? Trust me I would love to do TDD on an AI / big data analysis project. But the reality is that no-one has figured out how to reliably test things....so TDD is not the right tool at this point. But there is also the potential to introduce vulnerabilities. That doesn't mean I am not going to use AI or do big data.
It's always a balance between tighter security/less complexity, or more complexity and less security etc...obviously there are other factors as well, but my point is to choose the right tool for the job.....sometimes it is Rails, and sometimes not......
And beyond that give the Rails team kudos for a taking care of things like this when they do find them.