What you're talking about is a photon drive, which still obeys conservation of momentum. The EMDrive was (claimed to be) reactionless, and a genuine reactionles

What you're talking about is a photon drive, which still obeys conservation of momentum. The EMDrive was (claimed to be) reactionless, and a genuine reactionless drive would shatter physics at the foundations. In addition to the other replies, a working EMDrive would imply that the results of physics calculations would depend on your choice of coordinate system, because of https://en.wikipedia.org/wiki/Noether%27s_theorem https://en.wikipedia.org/wiki/Noether%27s_theorem, which would be absurd.