It may be harder than editing a Cargo file, but it is something you do once. They are some of the most mature and tested libraries in the world.
> wgpu will eventually also work on the web, so it's a great option for broad platform compatibility
OpenGL works everywhere today, including the web!
> In terms of efficiency (memory, battery, cpu etc.), the modern graphic APIs have more headroom than the GL-based ones
It doesn't matter for a pixel editor. Even if it did, you would have to do a very good job to beat the driver's GL implementation.
Otherwise, you may end up with something slower or buggier!
> Today, 4K screens are pretty common, and in the future, 144hz monitors will be more and more popular. If I want to render 2d graphics with no latency in those setups, access to the GPU makes things feasible
Perhaps, but again, GL allows you to do that.