Recently, I got into a debate on my concerns of the upcoming Inhumans film. It's possible and most likely, there will be important character motivations and plot points being introduced in Agents of Shield.
My concern is that this will make it hard for people who don't watch the show for whatever reason (and please, can we not have the you're a horrible person for not watching it or why not comments), to understand what's going on and this could be a sign of lazy telling. I was then accused of being a lazy viewer for not watching every little tie-in material, even works I don't like just so the movie makes sense.
I've always had the policy of that I'll watch/read tie-in material if I enjoy a work, I will not watch/read tie-in material just to understand what is going on. To me, that's a sign that the movie is not going to be very good as well as it being a lazy way to tell a story.
A good writer is able to quickly get all needed necessary information out there in a way that makes sure everyone is on the same level, but in a way that doesn't bog down the film. Star Trek 2 the Wrath of Kahn is a great example of this as it quickly explains why Kahn hates Kirk that in a way that feels natural and doesn't slow the film down.
I make it no secret that I do not like the Agents of Shield TV series, I've watched about 9 episodes worth and I didn't like it (which no, that doesn't mean I hate people who like it, it's just not my thing). Think if I went to watch a film I really want to see, Captain Marvel, only to discover that the villain's motivations are not in the film and to know why the Kree are searching for the Elements of Harmony on griffons, I need to watch an entire season of AOS. That would be infuriating. It would be like if you were reading the current Batgirl comics (which I am) but then a villain randomly pops and Barbara is doing something that doesn't make sense. Only to discover for me to understand all this, I need to read the Red Hood and the Outlaws, a book that that is well known to be awful. But that just makes me a lazy reader right?
Hell, we have seen in the comics that this is a really bad idea. During the mid-00's, DC made tons of tie-in material for their events and this proved to be a disaster. With events like Amazon Attack and Countdown where entire plot points and story conclusions were missing and both of those are heavily panned. At the same time, sales dropped for many of the regular comics like Catwoman and Wonder Woman that had their own stories put on hold for these events because readers didn't want to read about it. Hell, the 90s were even worse than this, with comics having issues 0s and having there plots end in other books all the time and we all know how well they are remembered right?
In short, tie-in material should be bonuses, not essential for understanding the film.