The actress -- known for playing Eleven on the hit Netflix series dating back years now -- dished her latest thoughts about 'ST' in a new interview with Glamour ... where she pretty much crapped on the gig that gave her her big break.

The article notes she likens her final season -- which is forthcoming next year -- to a senior year in high school, where one's itching to be done with it already. She says, "When you’re ready, you’re like, 'All right, let’s do this. Let’s tackle this last senior year. Let’s get out of here.'"

Millie adds, "'Stranger Things' takes up a lot of time to film and it’s preventing me from creating stories that I’m passionate about. So I’m ready to say, 'Thank you, and goodbye.'"

With that said, she does seem to offer a sense of gratitude for what she's learned on the show, going on to say the series gave her "the tools and the resources to be a better actor." And then, in the same breath ... another slap in the face, of sorts. Glamour says MBB refuses "to be goaded into mourning the show."

Millie finishes by saying .... "When it ends, I’m going to be able to still see these people," pointing out that nobody is actually dying with the fan-fave binger coming to a close.

Obviously, she's over it -- and perhaps for good reason. Out of all the kids, she's arguably far and away the most famous outside of 'Stranger Things' ... and it sounds like she's ready to break free from it completely. It has been 7 years already, after all ... so we kinda get it.