It starts off slow for sure, but that’s the Sanderson style. The end of The Final Empire (‘Mistborn’) is really really good and has a surprisingly powerful message behind it. The rest of the series kind of takes off from there. Well of Ascension was my favorite of the 3 but it FOR SURE is slow, mostly due to the main plot point with Vin, but I think that made it better because if the pacing was faster it wouldn’t have made the same impact
I felt the same until I read the third book. It took me a while to push through the series (which you shouldn’t have to do to enjoy a single book but I did anyway) and it made me appreciate the whole series more. Totally get it if you stop now tho too, the second books a little slower than the first, though the middle to ending third of the first book will significantly pick up in pace as well