Compared to hundreds of studies about green tea extracts, many of them reported by the media, those population-wide studies had minimal effects on the public. And even those studies would usually find the largest effects on people who drink impractically large amounts of green tea, e.g. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3103781/ or http://annals.org/aim/fullarticle/722554/relationship-betwee... (6 cups per day!). In addition, there are many confounding factors with population-wide studies compared to clinical studies.
Honestly its not impractical if you just replace your coffee with it. I probably average over 6 cups per day, and don’t really do it out of any health concern at all.
6 cups of green tea per day isn't anything unusual. There's always tea ready at home (my wife is Japanese). And at work I drink much more coffee than 3 (normal) cups. I don't drink coffee at home though. But I'm getting a lot of green (and other) tea instead.