But does it matter that the category of "active managers" achieves near-parity (after costs) with index funds if you're not able to maintain a running bet on th

But does it matter that the category of "active managers" achieves near-parity (after costs) with index funds if you're not able to maintain a running bet on the whole pool of active managers (i.e. you have to pick one or more specific managers)? For instance, if today's active managers always lose their asses to new active managers arriving tomorrow, then any active manager you actually give your money to today is going to do way worse than an index fund, not just somewhat worse due to costs. The set of active managers actually available at a given moment in time might be 100% long-term losers.