Clearly, Hollywood should be keeping an eye on the ENWorld boards, where everyone running multi-billion dollar businesses could discover they've been doing it all wrong for decades and the clear answer for how to create successful movies is to, um, adapt a previously created idea, preferably a D&D novel.
I cited Save the Cat because it's the most egregious example of Hollywood group-think, but if the fact that the book is older (although still very popular in screenwriting and especially production circles) is an issue, you don't have to look very far to find other examples, whether it's the "Die Hard but on a _______" genre that started in the early 1990s (and which gave us the excellent Speed and pretty good Under Siege) and continues today or the flurry of YA adaptations that followed Twilight (which gave us the excellent Hunger Games movies and the not so good everything else). Barring 2020's non-release schedule, it's common to see similar films coming out close to one another, because even the whiff of a good idea is enough to get other studios working on the same idea. Last year, I watched a whole slew of Netflix shows and movies with superpowers, all following in the footsteps of you know who.
But maybe fantasy adaptations are different. That seems like a bit of cheat, in that the thing that was once prohibitive for adapting fantasy (and science fiction) was the cost of special effects, has gotten dirt cheap thanks to CGI. There's certainly a lot of them being made nowadays, including ones already on our screens. We can argue about the ending of Game of Thrones, but it's hard to say the series as a whole wasn't a commercial and critical success. But Shanarra, also based on a wildly popular series of novels ... was not. Outlander is a big hit (and is likely only not considered a mainstream fantasy hit because of the gendered view of romance novels) while Legend of the Seeker, again based on extremely popular novels is ... again, not.
The lines of what constitutes a fantasy work and what doesn't are fuzzy and getting fuzzier all the time, but Supernatural, Stranger Things, Teen Wolf, Penny Dreadful, Fringe and Charmed all succeeded without being based on anything other than a name, an idea and good concepts by their showrunners. (Those are all over the maps in terms of quality, even between seasons, but they were all commercial successes.) And Xena, again while perhaps past some sort of statute of limitations, was hit fondly remembered decades later that was a spin-off of a TV series that had only the loosest connection to Greek myth. And Xena itself was more or less a hit out of whole cloth and much more fondly remembered than its ancestor.
But honestly, this is a pretty silly argument on an increasingly silly thread. There isn't a sure-fire way to create a hit in Hollywood, whatever the genre. It's not adaptations. It's not remakes. It's not chasing the trend of the week. It's not even hard work by talented people, because sometimes, for no reason that anyone can predict, or maybe ever identify, the audience just isn't there for the product.
No one working on the D&D movie or anything with a lot of special effects that have to be worked on over the course of months or maybe longer, is going to wing it without a sold script in hand. The amount of effort being put into any special effects-laden work is at least as much effort as is put into any D&D novel. (Oh, and RE, if you're super mad at me because I said D&D novels are bad and you're secretly a D&D novel author, I didn't mean
your novels. Not sure quite why you're so pissed at me, and it's not something I'm here to incite.) So adapting a D&D novel isn't somehow going to mean a more thought-out series bible than the film would otherwise get. (Now, if you're adapting Tolkien or Martin, or someone else who fills phone books with series detail, that's a different story, although even then, it has to be something the studio can work with; tossing someone 1,000 pages about the ancient history of a setting doesn't mean any of it is useful to screenwriters or directors.)
The D&D novels don't have huge name recognition out of gamer circles, and most of them are so far in the past, I think it's fair to say many contemporary players have never read them. I think we can all agree that the studio wants a mass market hit, not a niche success, and the brand name they'll be promoting is Dungeons & Dragons. I think the fact that they're filming in Ireland is probably most important for tax purposes, but it certainly does offer a ton of scenic locations. It could be the Moonshae Isles, or it could be Screenwriterpulleditoutofhisbutt Land. We won't know for a while.
I will go see the new D&D movie the same way I saw Pirates of the Caribbean: Curse of the Black Pearl -- nervously, but with optimism. It could certainly stink -- although it'll be hard to top the first one in that regard, even though it, too, has some nice bones in the form of the 3E setting that WotC appeared to have been toying with releasing, based on the snippets they posted on their website at the time -- but if it does, I have faith that the creators will have screwed it up all on their own, whether they adapt it from previously published work or not.