Desktop apps can reach higher quality. Compare e.g. Apple Keynote to Google Slides, the difference is obvious.
Depending on the features you use your argument might fall flat though, how do I collaborate on a presentation? How can I easily share a presentation with a set of folks?
I like Keynote a lot, but Slides has it’s use cases as well.
I agree GSlides has its uses. Web apps are good for ephemeral tasks, but I use desktop apps for stuff I care about.
1: https://support.apple.com/guide/keynote/intro-to-collaborati...
Fun fact: 2003 was Keynote's public unveiling. Before that, it was a bespoke NeXTSTEP app created for Steve Jobs. (I'm not sure how old proto-Keynote is, but IIRC he'd used it publicly since the late 90s.)
More here: https://apple.fandom.com/wiki/Keynote