I wonder if STAR TREK, with its (relatively) great dignity and seriousness, is what set off LIS's more heated detractors. Like, after you've seen Kirk and Spock playing it straight, it's harder to take Smith and his wise-cracking Robot. But if that expectation of serious sci-fi on television had not been created, maybe LIS would have been taken on its own terms.
I do not think it is a comparison to TOS which shaped the opinion of LIS. Think back to sci-fi TV from 1965-1968 (LIS' network run / high visibility)--in that time, not only did we see TOS, but The Invaders
and Irwin Allen's third sci-fi series, The Time Tunnel
. TI & TTT were played straight, often with grim situations one would expect from serious sci-fi.
Although both were not as successful as LIS, they appealed to fantasy fans (at least), and presented the polar opposite of everything which came to shine a negative light on the Robinson clan.
LIS was its own worst enemy, and whether the shadow of TOS existed or not, Irwin Allen's well known "do more"
directive to Harris (i.e. turn up the Dr. Smith behavior), playing up the popularity of Will & the Robot would have happened anyway, thus there's nothing to prevent the post 1960s criticism.