Competent entity systems are OOP, entity is synonymous with object (bring out some other object-like system, and a theasurus is usually used to find another word for object). You just don’t use classes, but there have been plenty of classless OOP systems since the Treaty of Orlando. Anything with a nounish tint will lean more OO than functional (of course, taxonomies are never perfect).
Objects have always been about modeling and design, a way to talk about a problem using language that is more similar in how you might talk about it naturally. Object-thinking is much more important than anything else. There are many different ways to spin this, but most game engines and simulation environments benefit from this in spades (and have ever since Simula 2).
