Sometimes the really hardcore otaku manga out there are criticized for holding back anime and manga, for catering mainly towards maniacs who want their series to look and feel a certain way, and in doing so restrict the respectability that comes with artistic variety. But as much as topics like fanservice and moe exist prominently in these sorts of criticisms, and as much as there’s the image of the anime fan with seasonal short term memory, I feel that having hardcore devotees of anime and manga allows certain drawing styles to exist in comics even well after their heyday has passed.
70s-style shoujo manga is called such for a reason, and unless you’re Miuchi Suzue drawing Glass Mask and you’re literally a 70s shoujo manga artist still drawing to this day, it’s hard for an artist to draw in that manner and succeed on a mainstream level, especially if they’re a younger artist. Sure, you could put some blame on otaku liking more modern styles, but it stretches well beyond that demographic to the average reader, and the otaku magazines also seem like the only places left where someone can draw 70s shoujo-inspired comics and be appreciated for it.

One example I can think of is the title Christie High Tension, a detective series centering around the niece of Sherlock Holmes. She learned the game from her Uncle Holmes, and now she’s heir to the name Jaaaames B- uh, in any case it has an art style straight out of that Candy Candy/Rose of Versailles vein, and it runs in the same magazine as Dance in the Vampire Bund of all things.
Certainly you couldn’t call it “progress,” as it’s more a kind of preservation of the past, but I know that I always feel a little sadness when I look back to older manga art, and ask where this all went. It’s not really about lamenting the changes that have happened to manga, so much as it is wishing that as trends develop, the old ones still don’t end up being forgotten, that manga continues to increase its variety.