Found nothing wrong with any of the other things you've brought up.
As said earlier, I feel that the characters aren't characters. They're cogs. Cogs for what? Drama.
Lucas is a straight man to the point of being an anal retentive asshole. He makes everything dramatic and freaks out about every fucking thing. Kid meets girl with literal super powers. Still doesn't believe her just to stick to his character trope. You can see this in the scene where they talk to the cops where the fat kid corrects Lucas on Mirkwood being from Hobbit rather than Lord of the Rings. Why? It's to establish Lucas as the straight man of the group. But his straight man peddling comes off as forced, why can't the kid let it go? Because he's a cog. So now every scene must have Lucas acting like an annoying dip shit in order to fulfill his role as straight man. But the show doesn't present us with a reason he's like this. He's just an asshole all the time and you're supposed to like the kid for whatever reason even if none of his actions make any sense. Time to start yelling and create drama!
Winona Ryder's character isn't even a character. It's a lady screaming "WILL! WILL! WILL!!!!!" over and over. Shut is giving me Lost flashbacks. "WHERE'S MY SON?! WHO TOOK MAH BOY?!" Winona Ryder not once ever stops being a crazy psycho mother. Here's another scene with her screaming! Another cog.
It's hard to articulate the difference between cogs and characters. It's subtle but it's apparent when I watch certain entertainment.
El isn't a cog. She has actual emotions and reasons for doing things. She's scared to go back to the lab. She wants to protect the boys because we have established that the science group will kill anyone who has any knowledge of her. Yet she wants to make friends and is earnest in her attempts to want to help in some small way. She is a genuine character who answers the why's and what's. The rest tho?
Stranger Things would be far better if it were only about the kids and the science shit ET style. Instead you've got all this other crap that makes it come off as schizo.