16:9 monitors are the norm now. And while this aspect ratio definitely works great for movies, I find wide layouts work less for presentation slides. Titles tend to get very loooong, and it becomes harder to make nice diagrams that usually call out for a 1:1 shape.
You might not realise it, but the slide headline on top of a traditional 4:3 slide actually created a slide canvas that is pretty much 16:9 below it.
Here is one way to deal with this screen aspect ratio: place the slide title to the left of the slide and use the full vertical space for the slide content next to it. What do you think?