Most of it has been said by the other replies and they're really good, adding a few things onto it:

- Would lead to reduced memory usage on the driver side due to eliminating all the statetracking for "legacy" APIs and all the PSO/shader duplication for the "modern" APIs (who doesn't like using less memory? won't show up on a microbenchmark but a reduced working set leads to globally increased performance in most cases, due to >cache hit%)

- A much reduced cost per API operation. I don't just mean drawcalls but everything else too. And allowing more asynchrony without the "here's 5 types of fences and barriers" kind of mess. As the article says, you can either choose between mostly implicit sync (OpenGL, DX11) and tracking all your resources yourself (Vulkan) then feeding all that data into the API which mostly ignores it. This one wouldn't really have an impact on speeding up existing applications but more like unlock new possibilities. For example massively improving scene variety with cheap drawcalls and doing more procedural objects/materials instead of the standard PBR pipeline. Yes, drawindirect and friends exist but they aren't exactly straightforward to use and require you to structure your problem in a specific way.