I don't think we can count the 'incestuous' storyline as a positive addition to the manga industry...
Going back to Banana Fish, the character of Ash helped to counter the trope of the fetishized pretty foreign blond boy who either was effeminate and cultivated in shoujo mangas or the submissive character in yaois.
Ash despite being a pretty boy is actually highly intelligent, physical strong and of extreme wits to be able to live inside the world of drugs and mafia and Eiji despite being a rather masculine boy is soft-spoken, gentle and despite being a damsel in distress, unlike Mamoru (ironically both voiced by Nojima) actually strives to stand on his own in danger and willing to die and kill for Ash should he be forced to.
It was one of the first positive depictions of male/male relationship in the history of manga with a whole manga centered around this relationship.
Moreover it was during a time when the rape trope was popular in yaoi mangas, and Banana Fish helped counter this mindset slowly but surely for today to have actually well-written Boy's Love manga as well as smut manga.
The main character of Ash has come in the Top 5 (over 100) most popular male characters several times throughout the 80s/90s up till recently.
When I'm talking about contribution, I'm talking about a significant concrete thing Takeuchi did (whether it was done before or not) and engrained it into her own work whether its via its storyboard, its story, lore or characters.
The Sentai Girl is a concept that she popularized but Mercury being the blue Senshi who is associated with water and wits as well as her character being most popular during the 90s anime in turn became a trope concretized adopted by several other Magical Girl shows.
Likewise, HaruMichi is culturally iconic but it's the 90s anime version that the cause not the manga whereby in Infinity they barely interact except during their intro chapter.
Fullmetal Alchemist was a much better written manga than Sailor Moon. The mangaka is even lauded as one of the best in the industry there's no comparison. Sailor Moon is a manga with 5 major arcs squished into 18 original tankobons with roughly 3.6 volume per arc. Any well written story-arc (of any genre) would take at least 5-6 volumes.
Yet, we did get a 1:1 adaptation of Dream via Eternal, was it interesting, fluid and satisfactory in the story department?
Yet, look at Bleach Bloodwar arc having 52 episodes announced or the Jojo anime that took 10 years but has now nearly 200 episodes and the adaptation still isn't over. Toei from time to time still continues to make yearly series like Digimon. Moreover, as notorious and vile Toei can be on the budget, they are always open to reboots of their shows - Saint Seiya, Digimon, Precure (which is a yearly reboot) etc.
Mark my words, after Cosmos is over, and if Takeuchi finally decides to move on after 1 or 2 years, Toei will announce a 52-ep TV reboot of Sailor Moon adapting the Dark Kingdom/Black Moon arc.