I guess your knowledge about rolling release distributions is very limited as well as about distribution maintaining and software developing. It’s much more complicated and time-consuming than deleting one line of code especially when the team is small and work on very limited resources. I suggest doing research in that topics.
What you understand by “improved”? Did a set of Manjaro tools, system and kernel tweaking are not enough? Besides, Manjaro its own thing it doesn’t need to be “better” or “worse” than Arch Linux.