The opinions on all the films (and all films in general) frequently change with time. That's just how human nature is. The original trilogy had it's critics (especially Empire when it first came out, and a significant portion of the fanbase hates Return of the Jedi), but people consider them classics. The prequels were initially cheered by fans at the time, as evidenced by people in interviews right after seeing the film. Some of them gushing like crazy. Then they became derided to the point that there are countless HOURS of film devoted to explaining in excruciating detail, why they are terrible and horrible pieces of cinema. Then the opinion seemed to shift to "eh, they're not great, but they aren't terrible, I've seen worse stuff."
The same is happening, and will continue to happen with the new trilogy. People grow older, their perspectives change on certain things. They see the plot elements in a new light, etc.
I had this very thing happen to me, quite glaringly with the movie V for Vendetta. I remember vividly, seeing that film in the theater, and hating it. Just being SO annoyed with it, mostly due to being still raw from the subsequent Matrix films being really bad in my opinion (at that time, haven't rewatched them recently to see if my opinion has changed). But I remember just growling in frustration and all the constant monologuing in the script. But then....
Years later, I found myself remember various scenes from the film in isolation, and enjoying them. A bit of good cinematography here, a fun bit of dialogue there. I'd pull them up on youtube and watch them, and enjoy them. And after like, 20 different little scenes like that I asked myself "wait....DO I actually still hate this film? Because it doesn't seem like I do." And so I rewatched it, and loved it. It's not perfect, no film is, but whatever issues I had with it, had apparently faded. Maybe it was simply getting older, maybe it was a change in my political/spiritual world views, maybe I was just going through a depression when it first came out back in the day. Maybe all of the above. But in the end, I had a fundamental change in opinion on the film.
I had the same type thing with the prequels. Going from really disliking them to just being sort of like "meh, they aren't great. I've seen WAY worse films out there. They have some good bits, but I won't go out of my way to watch them."
I suspect for a lot of people, a similar thing will happen with the new trilogy. And it's apparently already happening, as evidenced by threads like this one.