Some problems decompose naturally into functions.
Some problems decompose naturally into procedures.
Some problems decompose naturally into objects.
OO has extremely poor fit with functional programming at a fairly deep theoretical level. Procedural programming is often very useful for doing synthesis on a data set. Object programming is often very useful for people doing stuff to their virtual "things". The problem is when languages anchor to one abstraction or the other at a fundamental level (ruby) programmers tend to think they have to follow along.
In truth, it's about finding an abstraction (or set of abstractions) that fit the problem at hand. A lot of what makes OO hard is cases where one really needs to break down and say "but this bit? this bit is procedural" and having the experience to be confident of dropping the OO approach at those points.