True to it's roots It blows my mind on how critics and some viewers pan this series and clearly never read any of the source material. Being a long time comic book collector and fan. I can tell you that this series actually stays true to it's roots.
Casting, personally I don't think they could of gotten a better match without breaking the budget. The only one I would say is off is Karnak, having that big head and/or wearing that helmet. But I think this version is actually better. Gorgon is obviously changed races and a bit smaller, but this is not uncommon with most Marvel series lately. When you see each and every royal character, you immediately know who it is.
Story, this series could of been a great comic series. Which has a common theme to anyone who followed the Inhummans. Maximus takes over, the royal family flees, they work to get the throne back. Pretty much sums up most Inhumman story lines. The way they scattered them and had them find each other while learning earth's customs, is to me a fun twist. Though having Lockjaw (I love the big Doggie) teleport in random locations was the biggest stretch to me.
Effects, OK, this is where the series really loses people and I kind of agree. This isn't a big budget or even a moderate budgeted special effects series. I believe most of their money was spent on the actors. Black Bolts power obviously is gonna be seldom used and it's simple effect. Medusa, wow, OK, her hair looked cartoony and low resolution. But when they literally shaved the budget by shaving her head I almost laughed. Honestly I think it was series greatest mistakes. Karnak (one of my favorite Inhumans), his abilities are simple to CGI. Gorgon, OK, well they keep this one simple. Only shoot him from the waist up, on rare occasions shoot him from the waist down. In a blue moon, show him full body. Crystal, looks perfect, the rare occasions that she uses her powers they look great.
Final thoughts, the series isn't perfect by any stretch of the imagination. BUT, for what it is, it is actually pretty good. Stop trying think of it as a major marvel movie production. Thankfully they completely ignore the horrible version of Inhumans from the Agents of Shield series. Which I think has confused a lot of series watchers that never read the origin material.