But they're doing a similar thing with Justice League: The Snyder Cut right now though. I wonder why then?
Well, (1) the source is one feature film, not five, some feature-length, episodes of a TV series, (2) the main actors involved were available for reshoots, etc., because they are under contract for a multifilm franchise, (3) redeeming Justice League is more central to marketing further DC universe contebt than redeeming the last season of GoT is for marketing a prequel series with a different creative team, since the expected linkages are closer between the content, (4) it's also a reconfiguration from feature film to multi-episode mini-series, so it's optimizing for a different consumption format as well as “fixing” issues (in a hypothetical universe where external factors were driving business from serial streaming to theaters, reconfiguring the last season of GOT into a theatrical trilogy while fixing other issues along the way might make some sense.)
GoT is exactly what D&D envisioned. The fans didn’t like it, but it’s their vision, and they DGAF what anyone else thinks. We might not like that outcome as viewers, but should respect the artistry all the same.
PS: the cast of justice league didn’t dedicate 8 years of their life to making that film like the cast of GoT did. They’re understandably done and moving forward, not looking back.