You may want to focus on other schools.
Given your background, even with an additional year, I still think those schools are a big stretch (you're a middle-of-the-road candidate competing against folks with stronger resumes than you have; it's not just lack of extracurriculars, but everything taken as a whole - only thing that helps is you went to an Ivy).
Schools like Sloan, Booth, Kellogg, Columbia, Tuck and Haas are stretches - but schools where you have at least a shot of getting into; apply to 2-3 from this list.
Schools like Ross, Duke, Darden, UCLA, NYU, Cornell and Yale are sweet spots - schools where your profile is competitive and you have a more reasonable shot of getting in; apply to 2-3 from this list.
Schools outside the top 16 are safeties; apply to 0-1 from this list.
As for whether to wait another year or not, that's really a personal decision. I don't think in your case it matters that much - you may be a slightly strong candidate next year with 1 more year of experience, but not to the point where it will fundamentally change where you stand.
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