Rings of Power Made The Same Dumb Mistake The Hobbit Did
The Hobbit trilogy by Peter Jackson did not meet the benchmark, established by his earlier The Lord of the Rings Trilogy, for several reasons.
And one of the less disputable reasons was introduction of too many new characters – or effectively new characters, given that all the dwarves other than Thorin were barely distinguishable extras in the original book – about whom nobody cared. Giving them way too much narrative space, down to introducing side plots just for their sake, was a questionable decision at best.
But you can at least excuse The Hobbit movies by the mandate to make a trilogy out of a fairly thin book. There is no such excuse for The Rings of Power committing the same mistake.
Its showrunners, if they cared about their job at least enough to study reactions to Jackson's works, should have realized from the beginning that (a) they would have to write their own story from a rough outline and (b) original characters from Tolkien's lore would still be the main draw of that story.
Their timeline compression even provided them with enough of Tolkien's characters acting within the same period to form a fully developed cast.
Out of four main plotlines in The Rings of Power, two are filled almost exclusively by original characters (yes, The Stranger is obviously Gandalf, but he does not act the part and remains a walking plot device until nearly the end of the season). And in another half the cast are original, but that one we can forgive, because Prince Durin is one of the few good parts of the show and the story of Elrond's mission to the Dwarves at least directly ties into the main plot of forging the titular Rings of Power (even if mythril serving as a plot device is dumb).
But the Harfoot plotline has zero connection with the rest of the show so far. And the Southlands plotline had only a nominal connection – Galadriel dragged everyone else from her own sub-story to Southlands for reasons not even slightly influenced by what was happening in Southlands.
So, basically, not only about half of the show starts full of characters we don't know and don't care about (instead of, you know, starting with familiar names and faces, and gradually introducing new ones throughout the season); it is only tenuously – tenuously at best – connected to the rest of it.
That in itself would have been enough to alienate many of the fans who wanted to see Tolkien's characters first and foremost.