I'd say it's very relevant. The "Motivation and Scope" section bemoans the over-abundance of library choices and then declares that there should be one standard library for all developers to use. That's literally the situation in the comic.
> How many cross-platform 2D graphics libraries are there?
The document itself points out 4 cross-platform libraries. A simple Google search for "cross-platform 2d library" yields at least a dozen more.
> Also, the purpose is pretty obvious if you look at the use cases of Cairo and it's obviously not meant for (serious) game making ...
They explicitly state that they want to serve rendering of any type, including games.
No, the comic describes a situation with 15 competing standards. This is the first standard of it's kind.
>> The document itself points out 4 cross-platform libraries.
The document points out Qt, Cairo, GTK+, or SDL. Let's not count Cairo since this is basically Cairo. Qt is not GPU accelerated (nor is it a graphics library, Qt's graphics library is called Albert I believe) and GTK+ is not really a graphics library either and AFAIK, it itself relies on Cairo. So the only contender is maybe SDL (idk I don't know much about it, but it appears to be higher in the stack). And yeah, Google search does yield a lot of results. Similarly, if you Google for 'programming language', you will also get a lot of results. That does not mean that all of them are interchangeable or that all of them can be used for general purpose computing. If you are going to build a serious project, you will probably choose a platform with some support (such as a standard implemented by several vendors) behind it.
The only real contender that comes to mind is Skia (of the Chrome and Android fames).
>> They explicitly state that they want to serve rendering of any type, including games.
> How many cross-platform 2D graphics libraries are there?
The document itself points out 4 cross-platform libraries. A simple Google search for "cross-platform 2d library" yields at least a dozen more.
> Also, the purpose is pretty obvious if you look at the use cases of Cairo and it's obviously not meant for (serious) game making ...
They explicitly state that they want to serve rendering of any type, including games.