But do you keep track of how many people might not join because of the on-call? Or have exit interviews that check whether being on-call was a contributing factor?
If people don't join because of that, then I'd say that's a filter and I'm ok with that. In the Lisbon office of the company I work, on call was not a contributing factor for the people who have left. The vast majority was because they wanted to work in a different country, and not a problem with the company per se.