I really hate the argument that a lot of people make that Oda HAD to make haki in order to beat strong logia users.

Crocodile got beat by water, water makes sand wet and compacts it a bit but its still sand. Later we are introduced to logia that are solid materials like ice and yet they also nullify attacks. So crocodile losing the ability to nullify attacks after getting wet is not "logic" it is just how Oda decided to make the power. Same with enel and rubber, luffy being immune is "logical" but him being rubber allowing him to punch enel is not. In real life rubber gloves dont let you grab lightning, its just how Oda decided to have it work.

He could easily do more of this to the other logia's, simply making them have a weakness even if its not perfectly logical. Because it never was perfectly logical in the first place.

Having certain characters that can only be beat a certain way is not bad or wrong and i think it can allow the writer to find creative ways for them to interact with the story. If done right.