There is nothing wrong with a little humor as long as you can pull it off well. Lightening the mood is often welcome, especially in settings where the expected norm may be long, dry boring, content (such as a conference where people are attending session after session all day).
Besides making people laugh, a joke or two in an academic presentation can help make you and the audience more comfortable, make your presentation more memorable, and help you come across as a confident, competent presenter.
Of course, there are potential downfalls:
- A joke could fall flat, which may be awkward and embarrassing.
- Jokes that might come across as insulting can be dangerous (though gently poking fun at your own discipline can be fine--I have no problem with your proposed statement, especially if you make it self-deprecating, such as "I have made this slide extra complicated so I seem important". I have taken this approach and it usually goes down very well.)
- Too much humor can distract from your message. Use a little humor, and it helps engage people, and they will be paying attention to your serious point. Use too much, and no one will remember anything but the jokes.
But overall, I say go for it. Having a boring, forgettable presentation is a much bigger danger than a joke that falls flat.