I think a fair chunk of it is just nostalgia goggles, but there's also an earnestness that comes along with a lot of these early cartoons. Many of them were the first of their kind, so even if they were made with the sole purpose of selling you toys they felt unique and interesting to our young brains. There was also the subject matter. It's fair to say that most haven't aged too well and that as you get older their nefarious intentions are way, way more obvious. But I think that since so many of that early stuff was willing tackle difficult subjects without holding back too much it was easier to take them seriously. I'm thinking of stuff like, there's a scene in the G.I. Joes animated movie where Cobra Commander and Serpentor are having an argument and everyone's using this very verbose, heavy language that I, as a wee youngin', didn't really understood. I knew that they were arguing and I knew it was a power struggle but half the shit they said went right over my head. Like, look at this: Spoiler That's some pretty dense dialogue for a kids' movie, especially when you watch it in context. The whole thing is so dry, just a room full of people talking and being shits to each other. It's on par with the galactic senate scenes in the Star Wars prequels. But that dialogue told my young brain that these guys were adults, that what they were talking about was important, and made it easier to compare to real movies with real actors and real plots. Throw in some shockingly graphic violence (a guy gets stabbed in the fuckin' eye later in that movie)(the complete massacre of G1 Transformers in the animated movie)(half of what happened in Watership Down) and you've successfully tricked a child that what they're watching is pretty important and interesting. I remember that movie fondly even though it's a glorious goddamn mess.