I think you’re being a little harsh here. First off, why should Heinlein lose points for not predicting semiconductor computers? If you read his stories closely, he’s got computers all over the place, they’re just not called that: The library system in The Puppet Masters is obviously computerized; the majority of his early computers were based on the real computers of his day: large, bulky, limited machines. Excellent for number-crunching, but hard to work with. Like Brainiac, Eniac, et al.
As for your specific criticism about The Puppet Masters, it’s a little hard to claim it loses something to a latter work and make that stand up. It’s like saying that, to choose another example, H.P. Lovecraft’s Call of Cthulhu loses something because of Stephen King’s It. I understand how you can come to one before the other, but faulting the earlier work seems a bit unfair. 
(If you want a real kick-me-out-of-suspension-of-disbelief issue for The Puppet Masters, consider the unlikelyhood of an alien parasite being able to control the nervous system of an organism that evolved on a whole different planet. That’s always been the kicker there for me.)
As for the whole: “The world doesn’t work that way, so the story sucks,” argument: I think this is an entirely unfair criticism. SF, in particular, pushes the boundaries of what is known about the universe. By the very nature of that, authors are going to make guesses or stories that seem to fit what’s surmised so far, but doesn’t stand up to further examination. One of my favorite of Heinlein’s Juveniles is Space Cadet, and much of the action takes place on a jungle-world Venus. We know, now, that this is not the case, but at the time that it was written, this was the accepted explaination for the constant cloud cover over the planet. Other authors, paying close attention to the known theories made similar mistakes: Larry Niven talks about Pluto being the most dense object in the Solar System, and that the darkside of Mercury is the coldest spot in the Solar System, both of which are now known to be untrue. Arthur C. Clarke’s A Fall of Moondust, an excellent story and engineering puzzle, failed the test of reconizing the effect of vacuum welding, which means that the loose dust that the book depends upon for the whole setting doesn’t exist.
I guess I’m just saying it seems silly, when reading a ‘what if’ story, to dismiss the story as art, when the world it was based in has been proven to be just another Neverneverland.
For the OP, I’m glad you’ve enjoyed HSWT. And I really want to thank Jonathan Chance, again for helping you learn that all Heinlein isn’t as flawed as Cat. And I’ll suggest, too, that if you like these three - try Double Star, next.