On another thread on this forum (https://tibiantis.online/index.php?page=viewtopic&id=324&p=1#p1840) Lord has said that Windows 7 is the minimum supported version of Windows required to play Tibiantis. DirectX9 is supported since Windows 98. I believe we can safely say every Tibiantis player on Windows will have an integrated or dedicated GPU which supports DirectX9 or OpenGL. The same could be said for people playing on Linux or macOS. They will be using wine or some derived software which also supports those graphics APIs.

Removing DirectX5 as an option would lessen the development burden of keeping legacy unused options working.