Well, that's all a matter of opinion. I found it to be very tedious, and the only thing I "deprived" myself of was being put to sleep. In a four episode story, not doing anything interesting in one and a half episodes is unforgivable. I can't remember being quite so bored with a Doctor Who story as I was with The Robots of Death.
The "best developed society" thing sounds like a stretch to me. Besides the fact that not one of those things that the audience supposedly learn sounds the least bit interesting, if they actually waste time on stuff like that it would only make the story feel even longer and more tedious. Its completely unnecessary for a group of lame one off aliens. I enjoy well developed alien species, but for a one off species in a poorly written 70s Doctor Who story using time to flesh them out, but not make them interesting in the process, is stupid. It also doesn't makes me want to struggle through the story. The aliens were played by fairly poor actors playing irritating, one dimensional aliens that weren't particularly deep or interesting. I had no desire to learn about their society. I couldn't even stand watching them on TV, between the boredom and lack of them doing anything worth watching. I know enough about them. They're arrogant, stupid, most likely lazy and are very self centered.
Also, who the heck wants to get a science lesson from Doctor Who? Besides the fact that they usually border on idiotic (not counting the times where they leapfrog over idiotic and are just completely wrong), I'm not watching the show to be "educated". It's Doctor Who, not Bill Nye the Science Guy.
I'm also really unconvinced about the shows ability to talk about "examinations of mental illness and Post Traumatic Stress", especially with only two good actors in the story. I read the summary for this story. The culprit behind it is a guy who should have been in a mental institution, instead of going around killing incompetent, irritating miners. I can't fault him for his choice of victims, though. If only he had gotten to them sooner, the story might have been salvaged with The Doctor matching wits with a madman. Instead, we get a nut job who was apparently raised by robots (oh god that is such a stupid back story) killing generic aliens that I honestly wanted to see killed. My only regret is missing the robots take out a few more of the annoying aliens.
You're free to disagree, like I said above its all a matter of opinion. To me, its a story I couldn't get through, and spent ever second I was watching it wanting to do something else. I'm happy to move on and forget about it, except as the most boring Doctor Who story I ever tried to watch.
As you say, opinions differ. However, please grant that while I've seen this story at least a half-dozen times over the years and read the novelization, you never even saw it all the way through once. And it's often not until the fourth episode that some crucial story information gets revealed.
As for the science lessons - I said Leela
gets them. Not the audience. The scenes where the scientific principles get explained to her are part of her character's development from the "savage" we first meet in Face of Evil
to a less-savage individual who leaves the Doctor in The Invasion of Time
You may not have noticed a well-developed society, but again, it's subjective. Most guest characters in Doctor Who stories don't inspire any fanfic or musings of what happens in their lives before/after encountering the Doctor. This story is different in that respect, at least to me.