The more the merrier if you ask me. Eventually one will win but we need more experimentation in this space. The existing GPU APIs are too hard to use and/or vendor-specific.
Writing bits of Vulkan or D3D12 really isn't that bad if you're working within an engine which does most of the setup for you, which is nearly always the case for practical work. If you're doing everything yourself from scratch, you're probably either a hobbyist tinkering or a well-compensated expert working for a AAA game developer.
If you're targeting SDL, then you probably don't have an engine, or you are the engine.
Nit: there are also really sophisticated graphics engines for serious applications. It's not only games.
Using something like Unreal or Unity if you just want to blast a couple of triangles to the screen in a cross-platform application is a bit overkill.