Although it is 2021, there are sites that run on HTTP/1.1, and the owners of such sites have to argue for the need to switch to HTTP/2.
We will not describe the differences in protocols (you can read about this here), but we will share a link to visualize such differences.
On the page https://http2.golang.org/gophertiles you can see for yourself how much faster the HTTP/2 protocol is than the first version. To view results with different protocols and delays, use the links above the fun picture.
The use of a modern protocol is an condition for optimizing website loading speed. The issue of transition to HTTP/2 is decided at the server level by its administrator.