Actually, changing the line from "You should have reached out to me" to "Maybe you should have reached out more" is quite insane.
You're telling me they wanted to make it less obvious?
Because we only learn in the last episode of Season 4 that Mike was reaching out the whole time.
Meaning, the original scripted line "You should have reached out to me" implies that, perhaps...
Will didn't reach out at all.
Meaning Mike genuinely did feel like he lost Will.
(It also makes the line "That's because she's my girlfriend, Will" less acerbic because, from Mike's perspective, maybe that is the reason why Will didn't reach out as much. Since they're "friends," not boyfriends. How would he know what is acceptable behavior in this situation for two (best) friends? We can assume this is the first time a childhood friend of his has moved away.)
So, when Will says this—a line that didn't really make much sense to me the first time I watched the scene, THIS is what he's referring to. That not reaching out to Mike that we didn't directly witness on camera.
But, by doing that, he was, in fact, pushing Mike away. And he's aware of it.
It seems then that Will didn't first try to rip off the bandaid in the van.
He tried to do it after he moved, and he clearly had a change of "heart," which is why he was acting "weird." He was going back and forth.
Like, I know we already knew this, but it is nice to add another point to the "Mike doesn't think Will likes him back" narrative.
And, beyond that, it actually makes complete sense why Will pushed Mike away, even if it doesn't make sense to Mike himself. In the same way that Mike's actions don't make sense to Will, but they definitely do to the audience. (This is simply dramatic irony done well.)
Mike essentially tells Will that they are not going to end up together in his basement the rest of their lives (this symbolizes their intimate relationship), and that this is directly because of his relationship with El ("girlfriends," the reason things have changed from what they were, a previously very intimate connection).
Mike and El then break up, and Will and Mike's relationship grows close again.
They have a very flirty moment at the end of Season 3 in which Will promises his commitment to Mike (DnD is a stand-in for this), and Mike visibly blushes. They hug goodbye, and Will cries.
Will then finds out after all of this that Mike and El are back together again—and he can do nothing about it.
So, he just lost Mike even worse than he had the previous summer, after getting his hopes dashed once more. (He loses him once again to El, and he loses him to the move. This represents a very slow death to their relationship, a "slow-motion breakup," if you will, that is referenced with Jancy who is going through the same thing. Will therefore considers ripping off the bandaid completely, but goes back and forth on his commitment to the idea.)
If you're not convinced that this is possible, consider this:
Will doesn't actually rip the bandaid off in the van scene either, even if that is the scene in which the idea is insinuated. He actually started the scene with hope and optimism. His intention shifted when he heard Mike speak poorly of himself.
He is also shown visibly yearning in the pizza parlor.
So, when did he likely rip it off?
But that is not true, either, based on the events of the fifth season.
So, what can we gather from all this?
Will has tried to rip the bandaid off and failed each time. And the reason he has failed each time has been because of something Mike has done to restore his hope.
Well, if Will has tried to get over his best friend by "ripping off the bandaid" and failed repeatedly... So has Mike.
The Snowball, the rain fight scene, the Rinkomania argument, his monologue. Each an instance in which we see Mike try over and over again to shove his feelings down and move on fron Will with El, but he keeps going back each time, regretful, after Will rekindles hope. (Hell, even the script for him kissing El the first time in Season 1 frames his perspective as "there, I did it!" A lot like ripping a bandaid off.)
"I guess I did. I really did." / "Not possible." / "We used to be best friends." / "You're the heart." / *saves his life*
it is obvious that the writers wanted to emphasize the fear they both have of being honest about their feelings. Make it something big.
This is the misunderstanding trope on slow burn steroids, and I am here for it.
All this to say, the reason Mike and Will can't get over each other is because they both keep giving each other reasons not to. It is a back and forth that they are both responsible for.
Moments after Will "accepted himself" regardless of the possibility of Mike not returning his feelings:
(Mike Wheeler, I don't know if you should stand up or sit down.)
Now. The Duffers have said the ending they wrote felt "inevitable." And that makes sense.
If neither one of these characters are going to stop giving the other more and more and increasingly more reason to hope, eventually, that hope becomes realized. It becomes a reality.
And they are not going to suddenly stop this pattern of giving the other hope this late into the series, when the hope is amplifying the hope, again and again. It is accruing like a snowball, getting bigger and bigger. It compounds.
In the wise words of Hairspray, "You can't stop an avalanche as it races down the hill."
And that is the whole point! The writers are not stopping what they started, and it cannot stop at this point. There is a mutual misunderstanding-feedback loop getting stronger, like a signal that eventually reaches.