I was referencing the historical motivations that led to where we are today. Yes, I was referring in part to the SDL_Render family APIs. These were insufficient to support things like Nuklear and Dear ImGui, which are reasonable use cases for a simple 2D game, which SDL hoped to help with by introducing the SDL_Render APIs in SDL 2.0 in the first place.

https://www.patreon.com/posts/58563886

Short excerpt:

    One day, a valid argument was made that basic 2D triangles are pretty powerful in themselves for not much more code, and it notably makes wiring the excellent Dear Imgui library to an SDL app nice and clean. Even here I was ready to push back but the always-amazing Sylvain Becker showed up not just with a full implementation but also with the software rendering additions and I could fight no longer. In it went.

The next logical thing people were already clamoring for back then was shader support. Basically, if you can provide both batching (i.e. triangles) and shaders, you can cover a surprising amount of use cases, including many beyond 2D.

So fast forwarding to today, you're right. Glancing at the commit, the GPU API has 80 functions. It is full-featured beyond its original 2D roots. I haven't followed the development enough to know where they are drawing the lines now, like would raytracing and mesh shaders be on their roadmap, or would those be a bridge too far.