A lot of meta-analyses are done by residents. The quality of resident research is highly variable. I've read a bunch of it, I've conducted it, and I've co-authored it. Often they're too busy to care (which is OK - their job is a little something called saving lives!). I see "review" and I think resident. This is also seen as "data mining," or re-using data in a way that may, or may not be, similar to how it was in the original study. It's a method of analysis that's easy to abuse. My experience with the generally poor quality of these studies is the basis of my thoughts.
Systematic definitely reviews have purpose. Each chapter of the
Mont Reid Surgical Handbook details a specific area of general surgery and is written by residents. Residents summarize all of the relevant literature and become an expert on their chapter. They make great tools for learning and help the field. Maybe if you're the chief of surgery, and you've published the last 5 editions of a text, yeah it'd help your career in academia. But how did you become chief in the first place?
On hypotheses and meta analyses: What are you testing DKM? You're figuring out the "gestalt" that sums up what a bunch of people found out about a particular topic. But there's no testing. No controls. You might have exclusion criteria (e.g. "If a study was found to have insufficient power, the authors did not pool that study's data into the final analysis"), but there's no such thing as a positive or negative control in a meta analysis.
I have no idea what you're writing about DKM, and I have not read your work. I cannot judge what you've done, and my comments were not directed at your work. The OP asked for general opinions on relative stature of metas and whether it was possible to build an academic career solely upon them. I've never seen or heard of anyone doing this, and I would think it highly unlikely to do so.