To all creators of highly succesful adaptions everywhere
First, I'm proud of you. You did a marvellous job and brought joy to so many. You very likely expanded on the source material in ways that enhanced it beautifully.
But adapting is not creating.
Think thrice before you say "I can do this myself if I run out of source material."
No, likely not. Listen, I have every faith in your abilities as a creator. If you want to file off the license plate of your fanfic, go right ahead. Make something, twist it in different ways. Just don't think you can create official new content for your adaptions.
Game of Thrones is a recent example, but Call the Midwife suffers from the same ailment. The Handmaid's Tale. Yes, there will be occasional flashes of brilliance too, but it will likely still disintegrate like ratatouille without tomatoes.
The first problem is - there was likely a reason the creator stopped creating where they did. Cinderella 2? What on earth is there to tell?
Secondly. Your style is different. It just is. Probably your style harmonises beautifully with the creator's style. But if you take out an element - even if what makes the adaption succesful is the subversion of that element - it's gonna show. The lack is there, deafening in its silence.
The only way I have seen it work is if you essentially create a spinoff - take a side character that is compelling, but not necessarily only because of how they play off of your protagonist. I maintain The Handmaid's Tale, the series, should have become A Wife's Tale and focus on Serena Joy. Are there any secondary characters in The Queen's Gambit that merit their own story? I can only think of one, Georgi Girev - a teenage boy set to have everything the USSR can provide in terms of luxuries and status, but who can't quench his desire to defect. Hell, you can even have him face off against Beth Harmon again - with her now the unwitting antagonist, somehow blocking his path to escape or unable to help because that is not something she understands. But Beth herself? Don't do it. That's not your work.