You don't get to the level of Jeff Bezos without being smart. Amazon is not in the business of investing in failed ventures. So if Amazon is getting into the pharmacy market, there are two things to consider... Number one, they have to see real value in it for them, and Number two, they have to know that they can do it. So as to point one, the pharmacy market is a billion dollar industry, so yes there is value, and for point two Amazon obviously believes they can do it, or they wouldn't have bought Pillpack. Again, Amazon is NOT in the business of failed ventures. So YES amazon is a real legitimate threat to cvs, walgreens, etc. Besides, everything Bezos touches turns to gold anyway, so I have no reason to think otherwise that this won't work out for them.
Think that @YZXlnH2-1cpk gave a valid observation of this matter, worthy of its own thread.