That show was too goofy
Land of the Giants--like the other three Irwin Allen sci-fi series from the 60's--launched with a strong, very dramatic pilot, and a few memorable early episodes. Unfortunately, the Allen tendency to use the worst of his staff writers, trying to ape the Dr. Smith/Will relationship with Fitzhugh & no personality Barry, and other issues evetually hurt the series.
I will give it a break in that the running theme of a totalitarian government relentlessly pursuing all "little people" and their advanced earth technology was a breakthrough for TV sci-fi, and gave it an edge lacking in the other Allen series.
for anyone watching the series in broadcast order, one would think there some uneven development and a here now/gone later sense of danger. That could be due to the episodes not airing in production order. The start of the series seems stronger if you watch the pilot followed by the actual 2nd episode,
"The Weird World" which dealt with the Spindrift castaways encountering the paranoid, lone survivor of an earlier space flight, and their attempt to locate his captured ship.
BTW, that lone survivor was actor Glenn Corbett, who portrayed Zefram Cochrane in TOS'
"Metamorphosis"--another lost space traveler script.
One strong point for the series is that the characters had occasional conflicts, but they seemed to have a genuine loyalty / affection for the others, particularly the
Spindrift crew (Steve Burton, Dan Erickson & Betty Hamilton).