Yep. Mobile is the primary and indeed only way a lot of people access the internet now. Ludicrous that they just flat out reject those users!
Web design/development from the past 5+ years absolutely requires specific, deliberate, and thoughtful support for mobile users.
On a serious note: “Mobile-first” was a rallying cry a few years ago - but all I remember are pages that didn’t work well on desktop, especially pages with above-the-fold (`height: 100vh;`) full-screen graphics or worse: videos. It’s cute on a handheld 480x640 display you can scroll-flick, but terrible at 2560x1440 with a mouse-wheel.