That said, even for those uses SDL2 (much less SDL3) caught up to SFML about 6-7 years ago in usability issues for people without experience coding at that level. Circa 2015, SFML was the easier route to both performance and a working cross-platform binary. That hasn't been true for a long time now, even when SFML started to get refurbished around 2021/2022. The only times I've come across SFML since 2017/2018 have been projects migrating off of it and onto SDL 2 or 3.
It's good to have both SFML and SDL, among other C++ options and other-language frameworks. Even looking at 3.1, I don't think I'd recommend SFML now, especially not for the same reasons I might've done it 10 years ago. But it's good to see them modernizing anyway, and changes like this might make it easier to update and maintain old or abandoned projects that still use SFML.
What motivates me to work on SFML is, that we're building something separate from SDL. I don't think, we - as in the general developer world - do anyone a favor in consolidating everything into one library (why use X, when Y does the same?). Additionally, I think it's a very interesting "field" of trying to provide a common API across different OS; and sadly it seems to be an area where few resources exist and fewer developer actually understand it, as "everyone" just uses SDL. Finally, I really like the open and welcoming community we've built over the years and at the same time, I'm happy we're not getting as much attention/pressure as SDL.
Lately I've been doing the experiment of just forgoing the library entirely for this kind of code. It's a bit like gradually building up my own SDL/SFML directly in-place. I'm sure people would find that wasteful or odd, but I enjoy learning the differences in the platforms, and being better positioned to integrate with a particular platform. I'm also shipping way less code. Although admittedly I'm not sure if I'd do this if I were a C++ dev, I write Odin and part of the experiment is putting Odin through its paces and seeing how well it fits in this part of the stack (very happy so far.)