That'd be a huge undertaking with how much of the art in this game is "low quality." At least by my standards. About halfway through the game it seems like they started to only have the one artist, & they're... Not Great, imo. Shame the art in this game is so inconsistent. Some of it is phenomenal, & some is just.... not good. Guess they didn't wanna pay more than 1 artist anymore. Which is weird since i've seen some fantastic fanart of this game, so you'd think it wouldnt be That hard to find interested parties.
Well, they clearly listened to people pleas for uniform artstyle by hiring the only artist. The result, I agree with you, wasn't great - their current art is mediocre and, IMO, weaker than many the game already had. As you see, sometimes having a dozen or more artist while making artstyle inconsistent - I do not see it as a major issue, BTW! - also means that there is an art for everyone. And if you miss with the singular artstyle, then someone might be put off by the entire game.
The way around? Make sure the single artstyle you use is actually worth it. Claire's Quest and Overgrown (both games not unlike Roundscape, being RPG-maker products) managed to do it, for example. And I can't say their art is stellar - but its good. While current Roundscape art while not terrible is just... bland? Mediocre? It feels like those anime-sque porn drawn in 2000s, one where you could hardly tell one artist from the other. It lacks some... spark, I guess? Something that would make it a stand-out.
But what really draws the line for me is not how that person draws, but what. Very exaggerated and very poor range of expressions - most look like those stereotypical cheap porn movies where everyone is REALLY happy to see each other in most overacted way possible. "The Lusty Plumber 2: Backpipe clogging" limited edition only for 0.99 USD! And the artist draws each character the same way: muscular orcish war-girl, slim elven woman, farm milf - every girl would be a bimbo.
What was good in hiring many artists for many scenes is that they potentially won't have to work outside of their field of expertise or aesthetic taste. Which in turn could make their style fit the scene better. Take for example Farm Mom scenes: artist encapsulated well that she is an adult, a mother of many, so she is soft, juicy and maternal. Now one artist is doing all the work, and it shows that they struggle to do everything.
As for the undertaking aspect - well, they replaced less than a dozen pictures, IIRC, of few artists. And I'd say some were really some of the weaker artstyles, but then they replaced incredible art for ice spirit scene with current artstyle. I can't find the original art, sadly, but IMO it was both aesthetically and technically better.
P.S. On a sidenote, they did replace some pictures in the past. For example, Farm Mom had entirely different artstyle for her scenes, which some people thought was much better.