In my one year of university studies, I had a bizarre penchant for building slide decks in photoshop. I still think some of the slides hold up today, so here’s a few of them. I don’t think you can easily do gradients quite like this in Keynote today without custom art.
Truthfully, I haven't touched the .psd since about 2010. The similarity of the gradient colors is a huge shock to me. It's really cool that 2010 Alex and 2019 Alex have similar color choices, just with slightly different opinions on vibrancy.