He stated that in good old days people entering Yeshivos would end up doing “something for Klal Yisroel” like become Roshei Yeshiva, Rabbonim etc. This implies that if one only learns forever, he does not benefit Klal Yisroel.
I don’t think that that statement implies that at all.
This is clearly apikorsus as per Gemora in perek Cheilek in Sanhedrin.
Cite? Are you talking about “Mai ahanu Li Rabbanan?” The quote obviously did not mean that since he was talking about people who don’t become rabbannan.
The Wolf