With the amount of great unadapted stories in the Silmarillion, I don't know why they have to go for generic fantasy fanfictiony crap.
Give me The Children of Húrin, give me The Fall of Gondolin, give me Beren and fucking Lúthien... any of those would make for an excellent anime or live action series, if done properly with enough respect and funding...
Using someone else's work's name just to ride on their coattails because your fanfiction isn't good enough to stand on its own is a (sadly extremely common these days) massive red flag that guarantees I won't be wasting my time watching it.
There's legal issues. Embracer group owns the rights to make video games based on the lord of the rings and the hobbit, but the Silmarillion and unfinished tales of numenor is still owned by the Tolkien Estate, and they are pretty selective with it. The first age is basically off limits to everyone except Amazon prime right now.
The animation was done by Sola Entertainment, a Japanese studio. Though this studio appears to work closely with western publishers and IP for the majority of their projects.