Part of the problem is probably the Fortunes of Ravenloft card reading. It randomly provides 3 locations in which powerful artifacts useful to beat Strahd can be found, plus 1 possible ally. To keep with the spirit of this, I actually drew the cards randomly in advance, just making sure that none of the results would be counter to the way I wanted to run the adventure (you could theoretically end up with all 3 artifacts in the castle). But in hindsight that random drawing resulted in 2 out of 3 locations being places where I had other story elements leading the group there.

So I am still left with a few locations that the group has no reason to visit. And now I have to invent new story elements myself to lure the players there. One location was the werewolf den my players visited in the last session: I simply told them that the third gem of the Wizard of Wines vineyard was there. The written adventure tells the story of the three stolen gems that need to be recovered for the vineyard to be able to produce wine again, but only says where two of those gems are.

For Argynvostholt and Van Richten's Tower, I will change the story and add some new elements that fit with what actually happened in my campaign to introduce them. As I tricked my players into overthrowing the burgomaster of Vallaki for Strahd, I have a rich story hook that I can play on. Still, I must say that the various locations in Curse of Strahd are presented in a weird order, and with too few suggestions on how to string them together into one coherent campaign.

As a veteran DM and having played the Ravenloft adventure in different editions multiple times (I even wrote a 4E version myself), I appreciate Curse of Strahd's expanded Barovia campaign setting. But even for me this isn't "play right out of the book", but necessitates a lot of prep work. I really wouldn't recommend the adventure to an inexperienced DM.