Meta lets you pick an age range and gender for each creative inside one ad set
What to do: If you split ad sets only to send different creatives to men and women, or to younger and older buyers, test one broad ad set with per-creative audiences against your current setup. Advantage+ audience has to be off, so run it as a test, not a switch. If you use a buying tool or your own scripts, check they can read and write the new targeting_automation.creative_audience_pairing flag and the creative_audience_pairing_persona field without breaking.
Source: Meta for Developers blog: Choose an Audience for Each Ad Creative ↗