i think one of the things stranger things did best in the later seasons is the lumax storyline - like, to me, an amateur, that seems like such a smoothly written later addition that wasn't planned from day one but developed out of season 2 beautifully.
they introduced max and built a really good foundation and then when it was time to do season 3 and then season 4, they asked themselves: how would these characters react to the events around them and what effect would that then have on their relationship?
and one might think, well yeah, that's just how it's supposed to work, but i think it sounds a lot easier than it is, because to make it that organic and understandable so that pretty much everyone Gets It is quite the feat.
s3 has them quite lowkey, but it serves them well, because they're literally just kids - just teenagers being a little bit messy, but having fun together. their main narrative function in that season is independent of their own dynamic, but it has these touchstones where you'll get glimpses. and those are glimpses of a very Teen Relationship. but they don't condescend, don't make it seem like that's a bad thing, but rather it's necessary and relatable to a lot of people when they think back on their youth. sure, they're funny, but not at the expense of that real connection they found in s2. it's lighthearted. it shows them as stable and real and that's what makes what comes next so satisfying and heartbreaking in the best way.
because i genuinely think that the best narrative decision of s4 is reversing the focus back to let the two of them deal with the fallout. this cataclysmic event in max's life becomes cataclysmic for their relationship also. and it's so understandable and literally just their story taken to its logical next step. it doesn't have to be explained through someone coming up to lucas and asking 'hey, whatever happened between you two?' we know. how can we not know? everything about the acting and the lines makes it clear from the very first scenes what is certain to have gone wrong.
and then, they slowly, slowly resolve it. and in its resolution, in this horrific way of forcing max to confront all that she's hiding from, we get to a more serious, a more mature (by way of trauma) core of their relationship. and it's a tragedy. they deserved to have that s3 levity for years to come before life crashed in on them.
it's a fucking tragedy, but it's really really good storytelling. to me.