In the 1990s desktop computers had relatively small screens. We used tables to layout pixel-perfect 800-pixel-wide designs. Time passed and screen sizes got larger. We used CSS to layout pixel perfect 1024 pixel-wide designs. The iPhone arrived and we decided the internet had two sizes, desktop, and mobile. We used media queries to lay out a mobile layout of 320 pixels and kept the desktop layout of 1024 pixels.
We have functionally stopped there (excluding some adjusting of our preferred pixel widths). The average web designer still seems to have accepted that the internet has two and only two sizes. Overachievers may identify a third size of "tablet". Frameworks may give us a few more sizes that are largely ignored. Regardless, designing for more than two sizes was just too big of an ask.
I actually agree, asking designers to design for an ever-increasing number of screen sizes is unreasonable. In fact, I believe designing for two unique sizes is unreasonable. Instead, I advocate for a screen size agnostic web design philosophy.
The web is an inherently responsive (and even mobile-friendly) medium. Our idolization of pixel-perfect layouts led us to sacrifice what makes the web uniquely powerful, and we still haven't recovered. The way out is not designing for more screens. The way out is to intentionally design for the web as it is instead of accidentally designing for the (two-sized) web we wish it was.