This is sadly not true, since buisness apps use a much wider variety of windows APIs while games are mostly using a few (DirectX, OpenGL, Vulcan) APIs for most of what they do. You can see this with custom game launchers like League of Legends uses. The Game runs with basically native performance and without issues but the launcher is barely usable.
Plenty of key business apps use DirectX, OpenGL, Vulcan like CAD applications and games still use other Windows APIs. It's open-source, people can build off Proton to add the rest. These games for generally designed for Win10 now which support for is somewhat lacking in Wine. Concentrating on the latest version of Windows and APIs is a huge step in the right direction.
You're inverting the problem. The problem isn't that those things are used; the problem is they use lots of other things that aren't DirectX, OpenGL or Vulcan.
Don't get me wrong, such applications obviously profit from better 3D support in Wine but Proton won't make an impact on how well microsoft office or adobe cc products run in general.
