Let 'the baseline' refer to that level of well-being below which a life is not worth living. How's this for an inconsistent triad:
1) It's better to have a world that is moderately populated with flourishing people than a world which contains a huge number of people whose lives are barely above the baseline.
2) A state of affairs cannot be made worse by adding more people (all of whom are above the baseline) and leaving everyone else entirely unaffected.
3) A state of affairs can be improved by greatly benefitting a worse-off person at moderate (lesser) cost to someone who is better-off.
This is a concise version of Derek Parfit's "mere addition paradox". The problem is that if we start off with a flourishing population, by #2 we can add a further group of people who are less well-off, and then by #3 we can improve the welfare of the new group at the cost of the former. By repeated iterations, we eventually reach a state of affairs in which everybody is barely above the baseline. But at no step did we make the state of affairs any worse than it was in the previous step.
It doesn't seem that either #2 or #3 can be plausibly denied. But that means we are left with "the repugnant conclusion" of denying #1, and accepting that a swarm of dull (near-baseline) lives is better (or at least no worse) than a more moderate population of flourishing lives. Can you see any way out?