I think it’s very common to be honest. What can be thrilling on a first watch ends up becoming something quite different in the memory, to the point where you can convince yourself that you didn’t even enjoy it in the first place.
It’s similar to what we’ve seen with some of the recent discussions here of Civil War, criticising its choppy structure and unevenness of tone. The same people were effusive about it when they first saw it but have come to a more critical view with the passage of time.
(I was the same with Batman v Superman - I enjoyed it more than I expected on a first watch, but I’ve found that it’s only the bad parts that stick in the memory.)
If anything, though, with The Force Awakens I’ve gone in the other direction - when I first saw it I quite liked it but I found all the callbacks and references to the previous movies distracting and unnecessary. Now, though, I find that those things don’t leap out and bother me so much, and I find myself appreciating all the stuff that the movie did right in terms of reinvigorating the world of Star Wars and introducing a new generation of characters to the saga.