Eh, I think there is a bit of acting needed to try and convincingly play a man who is lost in his own past and loss, to the point of pushing everyone around him away, in a vain attempt to shield himself from further loss, by not making emotional connections. Otherwise it will look cliche and tropey. Just like you can do "plucky and infuriating child companion, that pushes the grumpy adult into feeling again, and living life" badly as well. It's all down to chemistry between the leads, and if they can really make us think they are portraying that role well. And you can absolutely do it badly.Joel is not a difficult character to play. It shouldn't be too hard to sleepwalk through that performance. Ellie is the tricksy one to achieve sincerity.