[listenallyall]

It's the opposite. This page is specifically made for people who do have time to spare. You don't go to IBM.com to find your next font -- you go to Google fonts or any font "buffets" where you can preview hundreds/thousands of fonts and pick the right one.

If you landed on this site, it's because you found IBM Plex elsewhere and decided to take some time to find out more about it. And IBM knows you have a choice of thousands of fonts, so it purposely wants to go overboard on the presentation, show you how much thought went into these fonts, and hopefully even make you a bit nostalgic or emotional.

It's also a typography presentation, anyone viewing it on mobile isn't really the target audience anyway.

[BitwiseFool]

You're right, I do sense that this was made for designers first. It's more of a portfolio demo than a font demo. The bulk of the page is graphics rather than in-depth text samples.

That being said, I still think its a poor all-around presentation.