Self replicating bots are feasible in some form, probably not in the one presented. Also, it isn't plausible that the rest of world would look as similar to ours presented in the episode as such technology would have many far-reaching implications on the rest of society.

Still, at some point you have to limit yourself. Having this one change and not change the rest of society makes it possible to imagine and relate to that one tech.

One bite sized chunk at a time.

Edit: Interesting example: What if we had teleportation technology that you can carry in your pocket? It's extremely hard to figure out all implications of this and if you manage to figure out how the world would look like it would probably be hard to relate to because it would change everything. So we have to keep a balance between relateability and plausibility.

I agree with you, it's walking a fine line between the two.

But in ways science fiction is in ways like chess - the author thinking more than one move ahead makes it more enjoyable.

There are many interesting topics to explore though.

For instance, I'd like to see a Black Mirror style exploration of a world where CRISPR use (on everything, including humans) is rampant and genetic evolution has become subject to memetic evolution, to cultural/technological/financial selection pressures. It's within realms of possibility with profound implications on everything

So let's say we'd make a Black mirror episode about CRISPR. What could it be about? Biomachines making most of our stuff including houses? Designer babies that glow in the dark and can communicate telepathically? Both? 10 other things? Let's choose one. It's difficult enough to imagine the social impact of that. If we choose multiple such inventions in one swoop you would have to make a lot of assumptions that each would be enough content for a single episode. Then audience will no longer be able to use what they know about today's society because they don't know what assumptions the author has made.

edit: I realize I might be overselling a point that you're already agreeing on...

yeh that was one of my favourites too

but thing is, nobody can predict which technologies are more of less likely to take-off, it's a mysterious thing but many smart people poo-pooed the internet, cinema, cars, computers