Linux will never be as coherent as Windows is. It's not just about theme. It's about the whole system. Windows was built from GUI. Linux is built from CLI and GUI is just incomplete buggy slap upon CLI tools. With myriad of choices it'll never be comparable.
Linux need some visionary company which will push hard on some sane technical choices without alternatives to provide coherent vision. It would require tremendous resources and it'll cause tremendous resistance from community (just observe how much hate systemd receives and it's still not as convenient as services.msc from Windows 2000). It's unlikely to happen, so that's why I think we won't have good things, because Windows itself lost its vision as well.
Linux need some visionary company which will push hard on some sane technical choices without alternatives to provide coherent vision. It would require tremendous resources and it'll cause tremendous resistance from community (just observe how much hate systemd receives and it's still not as convenient as services.msc from Windows 2000). It's unlikely to happen, so that's why I think we won't have good things, because Windows itself lost its vision as well.