If I developed a new browser today, my baseline graphics abstraction would be CPU-side pixel buffers manipulated by compiled (WASM/native) code. CPU rendering works equally well on past, present, and future CPUs, works with working and buggy and missing GPU drivers, works on every computer made in the last few decades, will never be obsoleted like Glide and DX7-9 and OpenGL, and is plenty fast enough outside of 4K or 144FPS rendering.
No need to develop a new browser, you can easily configure yours to disable GPU rendering. If you like things to be slow and inefficient. Personally I'm never buying any display under 1440p 120 Hz again and I prefer to run workloads where they're efficient, so I'll continue to use GPUs for graphics.
