Paper reading is one of the ways of learning what else is out there. You can substitute that with talking to other people. Which Feynman did a lot, judging from the stories in his books.
Actually, now that I'm thinking about it, it seems to actually be MUCH more efficient (if you have smart people to talk to): trying to find the good papers in the middle of the sea of publications/noise is a very time consuming task.
Publications from reputable journals are easier to find than to find smart people firsthand who are experts in the field.
Unless of course you're Richard Feynman, and you happen to know them because you all worked on the Manhattan Project together.
And, for the record, Richard Feynman did not do very much paper reading. I know, I know, a very special case, but I had to say it...