It's not a binary choice between opening up now and staying in lockdown forever. We could wait a bit longer with opening up till more people are vaccinated, to reduce the risk of getting an infection for everyone (don't forget vaccines aren't 100% effective). We also could decide the immediate harm of lockdown outweighs the risk of long-term effects.

It's a complicated situation, and there's likely no perfect answer. However, it's definitely not as black-and-white as "if they don't get sick, they don't get sick", and such reductionist statements don't help make an informed decision.