look, I've seen this play out a lot. A MCM partner can technically get your site into Google's ad network by sharing their own AdX or AdSense approval. But it's not a magic bullet for bad content or structural issues.
The real question is why you're being rejected in the first place. Most rejections come down to thin content, low traffic quality, or policy violations. Layering a MCM on top just masks the underlying problem-Google still reviews the overall experience. if your site is borderline, the MCM might help short-term, but you risk sudden suspension when they audit placements.
Better to fix the fundamentals: improve article depth, sort out navigation, add proper privacy and about pages, and build some organic traffic. then reapply. If you're still blocked after that, a MCM can be a legitimate stepping stone-but treat it as a tool, not a crutch.
that said, some MCM partners are solid white-label solutions for publishers with real inventory. just vet them carefully. a lot of "MCM providers" are just reselling low-quality remnant ads that'll tank your user experience