nostalgia getting you cheaper clicks makes sense, it pulls people in on emotion but those are mostly the curious scrollers not buyers. problem-solution tends to pre-qualify before they even click cause they actually relate to the pain point.
what i'd try is run nostalgia at the top to grab attention then retarget those clicks with problem-solution. let the cheap cpc do the awareness lifting and the second touch filter for intent. also check what your nostalgia leads are doing after the click... if they bounce fast the creative isnt the only issue, your landing page might be promising something different than the ad.
honestly lead quality stuff usually comes down to messaging match more than the creative angle itself imo.