You are absolutely right, MD. Indeed "δέ" can mean "on the other hand" in modern Greek too, but it also clearly can mean "but", though at least in modern Greek we generally use another word. In Luke 11:28 (not 26) the "δέ" most likely translates as "but" as would the same word in Luke 8:21. The "δέ" in Matthew is usually translated "yet" or "on the other hand". But bd, there is no intimation in the Greek that those who hear and keep the word of God are more blessed than Panagia.
Hey, I remember something!