I think he's right, actually. It rings true with what we see here in the Netherlands. People don't feel like they're "throwing their vote away" if they vote for a minor party, so politicians can't have a laid back attitude.

Yep and the coalitions are famous for exemplifying the concept of "poldering:" https://en.wikipedia.org/wiki/Polder_model

There are efforts to make this happen in the us starting locally and working up. The states are left to decide how they implement elections on their own with a couple of exceptions. There is a tragedy of the commons aspect to it though, as if some states adopt proportional representation but not others the ones that do not adopt it gain advantage. Ranked choice voting is taking hold much faster than pr in the us, and it is pretty slow too. It can happen though. Both are viewed as being left leaning, which doesn't really make sense to me.

If their minor party doesn't end up as part of the governing coalition, there's no sense in which people feel like their vote wound up having no effect?