Sometimes it really is best to minimize the artistic license and let the masters work shine through.
In the former, you could argue your own creative vision might be "better" (in the loose sense), given the lack of popular success of the source.
In the later, it'd be a fair amount of hubris to assume you can make something more beloved than Tolkien's works.
Hubris, arragance, etc. You're coming back to words that mean the same thing. Just because it's a work you personally are not familiar does not make it more/less egregious that someone has taken the material in their own direction from the original. It's just that you have a personal connection to the orginal and may or may not like the reworked version.
That's why Amazon paid $$$$ for the rights.
It's unreasonable to ignore that and claim that taking the same amount of artistic license with Tolkien is the same as taking it with something else.
It is objectively different to adapt a more popular and well-known work.
(a) Creative leaders (producer, director, writer) hired for these projects chafe at having anyone tell them what to do (and this especially includes the source material!).
(b) Creative leaders hired for these projects are typically not themselves fans, and do not elevate anyone who is a fan to a position of authority, and so lack even an awareness of the material. And critically, an awareness of what current fans enjoyed in it. Which is sometimes a feeling or deeper than just "these specific characters or places."
(c) As big budget projects, and costly rights acquisitions to start with, there are powerful committees put in place to keep creative on the rails, who are even more (a) & (b) themselves.
As a result, there is literally no one in the room with a powerful voice who understands why so many people liked this thing.
Say what you want about recent Marvel & Star Wars, but Feige/Favreau/Filoni seem to have a better sense and balance of "Why did people like this thing originally?" and "What will attract people who aren't fans?"