Because much functions as an adverb (in addition to being a noun and an adjective), the adverbial suffix -ly adds nothing, and muchly is a superfluous word. It was common several centuries ago, but in modern English much has taken over all of muchly‘s territory, and muchly has an archaic ring.
Examples
Although muchly is useless in modern English, it still appears occasionally, especially in informal speech and writing. In these examples, muchly could be changed to much with no loss of meaning:
Conyers supporters who doled out a cool $4,800 at the famous Palm restaurant in Washington D.C. landed themselves a muchly coveted ticket to Super Bowl XLV. [The Hill]
Just don’t let this not happen because someone is too lazy to change an old policy that does not recognize new technology – muchly improved waste water treatment. [Chatham Journal]
And these writers demonstrate how much may function as an adverb:
When healthy, though, he’s a terrific defender and a solid hitter, even if he doesn’t walk much. [USA Today]
The Stock Exchange will argue Millennium, which allows computer-trading systems to deal much more quickly, is crucial in ensuring it can compete with rivals and driving up revenues. [Express.co.uk]
