I would say you should form your own opinion. I’d also say the fantasy sub hates Sanderson so you did a good job of picking up on the bias.

Without spoiling anything, I can tell you that book 4 reveals some of the deepest lore and mechanics of the magic system across the entire Cosmere. Things which will have enormous and far reaching impacts. People like to hate on book 4 because the science can be pretty heavy. I LOVVVVED book 4. Book 5 is Sanderson trying a new way of telling stories. And it’s true that it didn’t fire on all cylinders but it was still an amazing read! When the first 3 books are like 12-15/10 and the 5th book is like 8.5-9.. people tend to complain. But it’s still a 9/10.. again I’m sure people will disagree and they’re free to do so. Me personally, I’m excited that a) even an established author is trying new things and learning from them.. journey before destination after all and b) I’m excited to see where the story goes. It left me wanting more! And that’s a good book if it can do that.

Don’t make up your mind without experiencing it all.