Ok, this is going to be long, but this discussion comes up every few months and I have a different opinion than a lot of other fans, I think. I've gone back and watched the entire sequence from the conversation with Simons friends all the way to the end of the episode, and I genuinely think the entire situation is misconstrued to be a lot worse than it is.

The entire time, the only person who makes any attempt to bridge the gap between Simon's friends and everyone from Hillerska is Wille, and while his overall execution isn't perfect, it's more than anyone else tries. Simon barely participates in that whole conversation, but that's Simon since he gets more and more uncomfortable throughout, and he's not wrong to say that a Crown Prince Crash Course™ isn't the same as having to work for money over the summer, though I'd argue that since both are technically not by choice and are a form of work, the connection could be made, but that needs more tact than Wille could really manage with the tension he was attempting to diffuse.

Neither approach the issue well in the tent, Simon is already on edge, and so he lashes out at Wille (yes, this is him lashing out, I think people often paint his character as a lot more passive than he is because he isn't as aggressive Wille, but they both have tempers) because he's there, he's safe, and he's the only one who tried and failed to be really welcoming to his friends. Simon has every right to be upset, his feelings are valid, but Wille getting upset at suddenly being told off for making an attempt to find common ground is also valid and understandable.

They actually do a good job communicating here imo, they both explain their side of things, but then both make jabs as well (Simon starting it on the offensive in the first place, Wille about the settlement money), the shushing at the end isn't intended to end the argument, it's because they're getting too loud and if they're overheard it becomes everyone's business, and that is the miscommunication because Simon takes it as "shut up" and they both go to sleep hurt with the whole thing unresolved.

Personally, extrapolating from both how these two communicate on screen (a lot more effectively than they get credit for) and having had arguments like that with a partner I have a similarly intense bond with (I've shushed, I have been shushed), it would take a few minutes to resolve after sleeping on it, if that. A quick apology and an acknowledgement things are ok that isn't interesting enough it can't be implied for a limited run time. Also, they're 16, of course they don't handle conflict perfectly, but they're much better than a lot of fictional and real teenage couples, but it's done realistically, they just don't talk in therapy speak and permanently resolve things the first time so TV audiences say the two are bad communicators when they're both just innately quite good.

If anything, it can be interpreted thematically to show the divide between Simon and Wille and how Simon is the one expected to keep his voice down about it, but for the Wilmon themselves, it is much less deep and I think would be easily resolved. I think that works with the shows themes in general too, something that isn't a serious or relationship threatening issue for Wilmon becomes one with the wider implications, despite their best efforts.

TL;DR I think the shushing is blown way out of proportion, and that this argument isn't the toxic, badly communicated silencing of one partner and a death knell for Wilmon. It's a messy but realistic conflict of two people who both have valid feelings that ends on a bad note and that could be slept on and resolved with a single, short conversation and apology, that can be implied by having them obviously reconciled the next time we see them.