IMO rails is a victim of it's own success. By being incredibly productive and easy to get things up and running, you don't have to reason about your data design as much, meaning you are more likely (not guaranteed) to throw together a bunch of badly related garbage.

People love to blame the language and the framework, but in reality once you're past the proof of viability point, it's usually worth taking the time to review some of those initial decisions... except now you need to GrOw! :)

The fact that it's rails is irrelevant. It could be any tool that makes you really efficient by never erecting guard rails.