Scientists aren’t supposed to agree on anything unless it’s been exhaustively tested, everything has to be questioned over & over, that’s simply the way science works.
Face masks are relatively simple to test in ideal lab conditions, but put those masks onto people out in the wild & you’re never going to be able to test exhaustively, there are far too many unknowns.
Therefore you can make a quick & dirty decision based upon a very simple question, “will face masks help to protect the public if used correctly”, the answer is “yes” but that covers everything from 1-100% protection increase. If used incorrectly of course it could possibly make things worse, for instance, if people imagine they have better protection that they really do with a mask on & enter a more dangerous situation than they would otherwise. This is where the “no” comes in.
The question would be better phased “as a scientist, would you use a face mask to help protect yourself” – I’m a scientist, based upon what I understand, know & don’t know, I would wear a mask in certain situations such as visiting a supermarket, or any shop, etc. I wouldn’t bother wearing a mask inside my car as I could use recirculate & put the air through the filters if I’m following another car/passing cyclists, etc.