Exactly. It's not too difficult to imagine replacing LaTeX for some fairly straight-forward documents. But just by casually browsing tex.stackexchange.com, you'll soon find out that people use LaTeX for an amazingly wide range of different things, and it's capable of serving many, many edge cases very well. To be on par with that is a very hard goal. Let's not forget, LaTeX has been around forever, and consequently has grown into an incredible complex and varied ecosystem.