Few sci-fi shows have been blasted with such vitriol as LOST IN SPACE, mostly in the 1970s by writers who loved STAR TREK. You even hear it to this day: when I showed my boss the Moebius Jupiter 2 kit online, he snorted, "LOST IN SPACE, a giant leap backward!"
I admit, there were times when I "hated" Dr. Smith and some of the sillier plots, but as an adult rediscovering LIS, I've been able to take the comedic side of LIS in the spirit it was intended.
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.