[29athrowaway]

OpenGL 1 was very straightforward, and if you want, you can still use it.

Recent version of OpenGL are more difficult. But compared to OpenGL, Vulkan is in an entirely different class of difficulty.

[exDM69]

I wouldn't call it difficulty, or even complexity. Verbose is more apt.

It's daunting for a beginner but for a seasoned graphics programmer it is fairly straightforward. But still really verbose.

[skocznymroczny]

It's not straightforward even for seasoned graphics programmers. It's definitely easier for them because they have good grasp on advanced concepts such as barriers, image layouts, synchronization (things you don't really have to deal with in OpenGL/DX11 style APIs), but even they make hard to debug mistakes in AAA games/engines.