Considering the show separate from a Tolkien connection (i.e., letting it stand on its own and not judging it for being different from Tolkien's books and stories), I'd rate it about 4 or 5 out of 10. Its biggest sin is that it's boring. Another big issue is that the main protagonist is unlikable. There are few other characters that you care much about, either. The writing is...uneven, at best, and outright laughably bad at worst (especially some of the dialogue). The story doesn't make a lot of sense, there are lots of meaningless divergences, meandering plot threads, plot armor that breaks verisimilitude, scenes that "have a point" but are way too much on the nose, and the "twists" are obvious to everyone (except the characters in the show, of course). The acting is not great, either, but I don't blame the actors in this case; I think it's poor writing (and poor dialogue).
When you add in the Tolkien elements it just goes from bad to worse. Terrible casting is a stand out. I'm not talking about casting for the invented characters (they're invented, after all), but for the canonical characters. Some of the greatest figures of the second age (e.g., Gil-Galad, Elrond, Celebrimbor) are cast (and written) as complete dorks. Heck, Celebrimbor doesn't look like a powerful Noldo of the line of Fëanor (or any other line of elf, for that matter); he looks like an old man wearing his grandmother's drapes as a robe. Then there are the timeline oddities and other changes from canon. I could go on at length, but I'll spare you. I understand that a different medium (e.g. TV or film vs. books) might benefit from some alterations, but when that's done it should serve the story, it's tone, etc. in the new medium. The divergences from canon in this show aren't like that at all; they're just kind of thoughtlessly done, even where they're not necessary. Given their approach, I think Amazon should've just skipped the entire Tolkien connection and done their own fantasy show. This thing is about as "Tolkien" as one of those Xena or Hercules shows. Even the show's apologists have started saying stuff like "you need to consider this show as a new or variant story in the overall mythology. It's not trying to tell exactly what Tolkien wrote." Yeah, no kidding. And don't get me wrong, I don't object to original characters and new stories; I think there's plenty of room for that. But I think such new stories are best told within the established framework, doing no damage to the themes, tone, major characters, known 'canon,' et cetera. If you're going to just do your own thing and largely ignore the details of the canon/framework, then why use the framework in the first place? (The only reasonable answer I can come up with for that is to use a popular "brand" for marketing purposes.)
Anyway, this is getting longer than I'd intended. Suffice it to say I really wanted this show to be good. Sadly, it's just not. It's a missed opportunity for something good and worthwhile. Disappointing.
To end with something positive: some of the visuals are nice.
