Opinions vary on OOP being a mistake. Most likely people with that opinion are responding to the influence of Java's popularity in the past. Or the confusion with how Javascript was prototype-based but with Java-like syntax and then it got classes for further sugar coating.
I don't think anyone who regularly uses Ruby or Python thinks OOP is a mistake, it's in how you use it and whether one likes the OOP design of the language.
I don't think anyone who regularly uses Ruby or Python thinks OOP is a mistake, it's in how you use it and whether one likes the OOP design of the language.