I mean, in an app that uses Rails by-the-book, you won’t even find a class instantiation. No call to new. You won’t find a class that does not inherit from a framework bass class either. The framework handles everything, don’t worry.
A carpenter who only knows how to use a hammer isn't a very good carpenter.
And before you say "a carpenter can switch from DeWalt to Makita just fine": that's why the analogy was made with a hammer.