> DirectX is losing ground too thanks to Proton and Vulkan

[citation needed]

My understanding is that Proton is effectively a distribution of WINE + DXVK, which does for DirectX what WINE does for Win32. Valve is even on record saying "make one good copy of your game and trust our compatibility tools to port to other platforms" which is effectively saying "use DirectX if you want - Proton will run it just as well."