LibreOffice Impress is horrifically bad. The Undo function is unreliable which is an enormous data-destroying pain in the ass when editing a presentation. The tools for editing text and vector graphics are also inconsistent and buggy.
No offense but "ew". The demo page is hideous and I don't see how you can easily do graphics with that. Maybe it's fine for making slides for people to look at later, but for actual presentations slides, that looks like a recipe for PowerPoint hell.
I guess if you use impress/PowerPoint to do you graph, which I don't.