Are you familiar with Phillip K. Dick's letter to the FBI (1974) accusing Lem of being a Communist committee that had infiltrated the Science Fiction Writers of America? Because he was too brilliant, too widely educated and wrote in too many different styles to really be a single person. Yup.

As for Heinlein -- I, too, read and loved Stranger in a Strange Land as a teenager. But even at that age I was weirded out by his habit of making sluts of all his leading ladies, and having them make babies with their fathers, or father figures (read: Heinlein stand-ins). This shit is just gross, my dude. And the older he got, the hornier his female characters became.

Asimov, Bradbury, Michael Moorcock, JG Ballard. Le Guin. There are dozens of writers whose place in the cannon is ahead of those two.

That's my opinion and you are welcome to yours.

At one point he was one of the best sold sci fi authors in the world - in any language, at least judging by the liner notes on some of his older publications. I assumed that’s why his books were translated to English so early and so well. But I agree! These days his works are not as much looked at and read as they seemed to be in the past