Not just for Lost in Space, but for most sci-fi shows except perhaps much more recent ones.
That's of course within the structure of the show, that being individual families traveling through space.
It's realistic in that the not only do the Taurons not conveniently speak English (and no magic tech auto translates), they don't speak at all, so the Robinsons can't communicate with the Taurons except by making gestures they hope convey the meaning they intend.
This aspect of the Taurons makes them seem truly alien without any sorts of prosthetics.
Real wars have started in exactly this type of scenario, where misunderstandings, nervousness and minor mistakes spiral out of control. The climax is incredibly tense.
Also, the Robinsons never really know what the Taurons thought happened with their kid.
The script is intelligent in that they discuss these issues. It's a very nice touch that they deduce the Taurons device is an environmental probe (because it's collecting rocks). It's also a reasonable conjecture that the Taurons might be on a similar mission as they.
Yet ultimately the Robinsons do not know what the Taurons were doing.
Other notes:
I saw this when I was a young child in the 70s and remember the ball very well!
Smith still has impressive technical skills--- he had only partly morphed into his eventual buffoon self at this point and his character still had shades of his original role as a highly skilled spy.
Also, Smith's reasoning regarding the Taurons leans to the pessimistic but his concerns aren't silly.