Make No Assumptions (or Demands) About the Screen Resolution Used by Other People
On the Web, "webapps" are an abomination. They're like "Adobe Trash (Flash) reborn". For instance, YouTube abandoned Adobe Trash; but now it's a "webapp". It is in many ways useless. The same is true for X/Twitter, which in 2020 abandoned its non-webapp ("mobile") edition.
Many Web sites have effectively become "webapps" due to excessive and unnecessary adoption of JavaScript. Many sites also have a "mobile version" because they want to think that, rather than make some universal thing that works for everyone, they need different "editions" (or styles) for the same thing.
statCounter sees a very board range of resolutions, probably because of various models of phones (360x800 is the most common resolution other than 1920x1080, which is common on desktops and sometimes laptops too).
Techrights has a Gemini Edition but not a mobile edition because it's made to work with many types of devices, unlike "old Techrights" (which typically assumed a screen 800px wide; that design goes back to 2006).
There are usability aspects, aside from accessibility aspects. We need to get back to a Web where browsers are instructed to render pages based on descriptions of layouts rather than execute JavaScript programs and render "widgets". █