The people using Keynote (wholly owned by Apple Computer Inc.) never had to deal with this kind of heckling, I noticed.
I developed the HTML slides after a particularly hair-raising episode: I had been subcontracted to give classes at a large investment bank, and been provided with class materials in the form of a PostScript file. I spent the thirty minutes before the class frantically sneaker-netting a PostScript reader to the 1980s-era classroom computer, and then hand-editing the raw PostScript to keep the reader from displaying the slides upside-down.
After that I said “Never again. Every computer has a browser that can display HTML, so I will do my slides in HTML and display them in the browser.”
This worked perfectly, and had unexpected benefits. If I got to the venue and discovered that the people in the back of the room couldn't read the text, no problem, I'd just hit control-+ a few times and let the browser take care of it.
Using HTML also makes it easy to stick the slides on my web site for the whole world to share and enjoy, whether or not they have Apple™ Keynote™.
I've never regretted it. Slides I wrote in 1994 still work the same, without change or update.
https://perl.plover.com/yak/