Ridiculously long functions are a maintainability problem but so is a ton of really small functions that do not provide a logical separation of concerns.
OO code can provide modularity which can greatly improve the ability to make changes without breaking other code. On the other hand, when applied poorly it can have they opposite effect.
OO code can provide modularity which can greatly improve the ability to make changes without breaking other code. On the other hand, when applied poorly it can have they opposite effect.
It's not the concepts, it's how they are applied.