alot of critical parts of a game engine are already made in c or c++, and mono(the default stand for closs plataform for not engine user is not compatible whit rust)
one te driver tend to be write in c or c++ make it mor reasonable to use the same langues, ogre3d for (c++), heaps( for haxe i love it compiled to c++), mono(for c#/ c++), raylib (c/c++), i dont know why you want spend at of time in make a engine that need some of this frameworks, whit weird interface to use rust
it seam awful, the templates are the fucking same as other platforms, as person in business i would say i dont care which technology make the job if the job is done, in general this is define for the lowest price posible or for advertising, maybe make price for use the service and export to third party hosting but i don see this, knowing that WordPress is free and have a bunch of cheap labor who can tailor your website and host in a cheaper host