The 16:9 format was invited for movies not for presentation slides. Over the past 500 years, there is hardly any print work in a wide 16:9 format. Text that spans a wide column is hard to read, and most diagrams, paintings, visual concepts are more square than rectangular.
If you want to design slides in a 16:9 format you could consider breaking some of the slide design conventions. Examples: putting a multi-line slide header at the top left or even bottom left of your slide, saving up valuable vertical slide real estate. Or maybe even simpler: leave a lot of calming white space on the left and right of your slide.