I hear people say about their presentations, "I just wing it," or "I never practice."
Maybe they throw the presentation together the day before and go over it once, briefly.
They say, "When I wing it, I do okay. I don't need to practice it."
Remember this? "It's not about you."
What does your audience think about your thrown-together presentation? If you're doing the bare minimum to get by, then they're probably not getting much out of your presentation. You're basically showing the audience that you don't give a crap about them.
What's the point of giving the presentation if you don't care what the audience gets out of it?
Why be just "okay" when you could be "good" or even "great?"
If you're doing your best, and trying your hardest, and making a sincere effort, your "okay" is going to be better than someone else's "good" if they really don't care about the audience.
I'm not even talking about your skills here. I'm talking about your enthusiasm for your topic, your willingness to meet the audience where they are, and your desire to give value. Which means organizing, preparing, and practicing.
If you aren't willing to take the time and effort to do this for your audience, don't give the presentation. Don't insult them, and don't waste their time by being "just okay."