I'm giving 5 stars instead of 4 (honest answer) because so many people are downplaying this show. The one thing I hated was that stupid whip lightsaber thing. That was dumb. Other than that, I get it. It "messes" with cannon. But not really. If you think about it, everything that happens in the show is still possible given what else is cannon. I'll explain later. The writing of this show is solid. Good dialogue, great story line, and excellent fight scenes. The lightsaber battles were top notch. Characters, and character development, were both solid given the run time of the show. Honestly, better than ep. 1-3 Now to be the contrarian,
Spoilers ahead-
The reason this show doesn't mess with what is cannon, is that everything in this show was "on the dl" so to speak. There is a scene during the meeting of the Jedi where they even mention that they want to hide this to avoid controversy. So it's not unfathomable that no other Jedi would know that this sith existed. Everything else is well known. Jedi tried to basically genocide the witch covens. That is Lucas era cannon.
Overall, great show. Happy to have more star wars. 7 or 8/10. And anyone who wants to argue that this show was trash can debate me. I've read more star wars cannon than I care to admit.