Honestly? I think the main reason that stranger things ended up so horrifically was because they tried to do everything.
They couldn't decide between having a show that was mostly allegorical and metaphorical for being an outcast in a rigid small town or being a surface level sci fi so they flip flopped on both and FAILED on both. They ended up setting up so many meanings and using that to send the absolute wrong message.
They set up for the mf/vecna to be an allegory for abuse then they turned around and said that Henry needed the mindflayer. Needed his 'abuser'.
They set up that there were some people who are so worried about perpetuating abuse that they think the only solution is to kill themselves. And then they killed them.
I'm not even mad about Byler (I am but the other things are important to mention) but even that they set up through parallels and lighting and costuming. And then they turned around and didn't even EXPLAIN IT
Chuck got Jimmy out of jail, he shortened his sentence but he "shouldnt have". Jimmy got out without concequences and he wont change, hes not worthy of being a lawyer with the name McGill.
Jimmy rejected the 7 year sentence in favour of the longer one by telling the whole truth and accepting the consequences and he took the name Jimmy McGill back .