This post contains spoilers for the whole season.
Well, I think that it was watchable, but IMO it was just kind of dumb. The series lacked ingenuity and in some places was just stupid, and the pacing was off.
Bringing back Gandalf and the hobbits was too fan-servicey and too slow (I assume that they can still change it later to one of the other wizards), the whole Mithril plot was just dumb, as they basically didn't explain why the elves are dying and afterwards didn't explain how the rings fix things, Durin's plotline basically meant nothing in the end as they just managed with their original nothing amount, Celebrimbor is supposedly the second best smith ever doesn't even think on how to improve alloys and as they wanted the Wizard to be "Sauron" bit, the nothing plot-line of the Harfoots to end with a rush on the last episode.
I liked Adar as a villian, I liked Arondir and his plotline mostly, and the whole Dwarves plotline as well (Especially Durin). They should have, IMO, just went with a more robust Mithril/Elves/Dwarves plot-line and southlands plot-line, and have the orcs returning make the southlands go to Numenor for aid. If they really wanted Galadriel, maybe have her pop up in the southlands once the Elves hear of Adar, thinking that he's Sauron. Sauron, IMO, should have already been with the Elves in some advising capacity, pushing for the creation of the rings. Once Sauron reveals himself end the season with a comet hitting the earth or something, but that would have ruined the "You're Sauron!!!" bit.
I do think, however, that things can be fixed, and LOTR has a lot of things that can be done inside of it even without The Silmarillion content. A lot of shows had way worse first-seasons and became great. There is a nugget for greatness, they just need to hold back on the fan service (Harfoots Hobbits, Gandalf, Balrog, too much Galadriel).