Ghostbusters had reason to be complained about for doing things that even the Witcher did not go as far doing. Ghostbusters had an identity issue after race swapping the main cast and replacing character archetypes entirely. It didn't actually do its own thing or try to create something new, it was too hung up on trying to capture the spirit of the original in a 'what if they were genderswapped into sassy, independent women' way.
People aren't complaining about Witcher because the characters represent the same from the books and are generally played out the same way. Rings of Power is getting flak for how it's chosen to adapt characters, like what we've seen with Galadriel.
This is why diversity isn't really the only issue here. Rings of Power has an identity crisis overall with diversity being the least of its problems.