The whole idea of "seasons last many years so winter can be a long ways off but when it hits, an entire generation grows up in darkness and cold".... uh.
Let's ignore what it takes to make a planet do that, okay? Wave the Plot Wand and declare you've got the right rotation, distance from star, axial tilt, interference from ancient deities, etc. to make that happen. Fine.
The resulting flora & fauna would not look like earth plants and animals. You would not have "harvest season is 2 months out of every 12" if summer lasts for multiple years; there'd be no push for plants to get their seeds grown and ready to be in the ground in a couple of months. Plants could grow much more slowly - but they'd need a hibernation ability to survive winter, not just "they kinda go dormant for 12-ish weeks."
Animals would be even more affected. Years-long winter means you can't just scrounge for scraps, lose a bit of weight, and wait for spring. More omnivores, fewer herbivores, and a lot more long-term hibernators. Potentially, lots of "herbivore in summer; carnivore in winter" animals.
Potentially, a number of plants and animals that only thrive in winter and manage to go into deep hibernation or seed/egg stages during summer. Hey, they have less competition.
I don't even want to think how bugs would work. The mind boggles.
The resulting human cultures would not look like European middle-ages-ish cultures.
GRRM's cultures are European-esque factions thrown into a fantasy/scifi setting that is impossible to allow those political factions to form. There's endless weird handwaving past things like: why would people call it a "year" when it's been summer for seven of them? What do they use to mark "years" as we understand them?
Why would you even have four recognized seasons? If this were a colony world like Pern, then maybe there's an ancestral recognition of year-cycles with seasons, but if summer has always been 7-10 years long, why would you call that "summer?"
All of human culture - entertainment, travel, political machinations, city infrastructures, language, food, etc etc etc - is affected by Earth's cycles and seasons.
Martin makes a few changes here & there to deal with his extra-long seasons and pastes those into a fantasy-ish European backdrop with no attempt to make things consistent.
(And that is FINE. It's a fantasy story. You're supposed to be able to handwave past a lot of the implausible things - not worry about how widespread writing skills are and who the scribes are if there's no equivalent of a Catholic church with monk archivists; not worry about how they have certain metal tools but no printing press or guns; definitely don't think about the sword technology plz. Readers are allowed to say "hey I'm enjoying the story; it doesn't have to be realistic.") (Look, a whole generation lost their minds for teenagers who could waves sticks around and levitate tables.)
But. The fact that it doesn't need to be realistic to be good writing (...another debate we're shelving for now) does not mean it's "realistic" because the outfits resemble those in historical dramas.
Frozen has more realistic politics for its setting. More authentic technology. A more plausible culture.