I'll wait more. There's nor two years since the game was released, so it can clearly be the explanation of tools not existing to advanced things to be a thing yet. As @Cinossu mentioned, this makes me remember the very past of the Sonic rom-hacking scene where tools were very limited in what it refers to the variation possibilities. Though I can't judge it for the present instance because it's still too early for this. It's obvious the Sonic Mania modding isn't a replacement for the rom-hacking and it doesn't seems to be a replacement for the rom-hacking in the future, but I'll wait because I know it could be a good alternative for the ones who doesn't want to deal with binary stuff. It's just a matter of the time for tools and stuff to be developed. Especially because creating a engine all from the scratch would be way harder than editing a existing one. All we have to do is to wait for the time to pass so we can study the game's engine for develop the proper tools.