I'm not disappointed, a continuation after Sailor Stars would have been ridiculous, there's almost no story left to tell, they fought villains on a galactic scale, they showed the past and the future of the Sailor Moon world, a ton of characters had been introduced and their relationships explored in countless episodes.
A back to basics approach and doing a new adaptation of the manga is the only way this new anime can realistically work, barely anyone would have cared about a post Sailor Stars story. Seeing Usagi grow up, change, learning about her destiny and meeting the other senshi, falling in love etc. is the interesting part, why would a new anime not do that and instead make a show were she already knows everything and just keeps zapping monsters until it's time to become queen? Her character's journey was complete after Stars, she was the most powerful senshi in the galaxy, surpassing everyone else.