Good review, much appreciated.
Your point about watching it in short bursts is an important one. These stories (from 1963 to 1989) are not meant to be watched in one go. They are serials, not movies. Watched an episode at a time, as they were meant to be seen, a lot of the criticisms made regarding slow pacing, or six parters that 'sag' in the middle vanish. Watched weekly, or daily, these stories work. And it should also be remembered re pacing that in 1965 this was not a 6 part story, it was 6 episodes of a continuing series, one in which the audience did not know how long each particular adventure would be, or where it would start or end. All of which makes a huge difference to the viewing experience.
In regard to Web Planet, there are definitely aspects of this story that are pretty silly but, as you say there is a genuine attempt to create a wholly alien environment - this is a daft, but incredibly ambitious story and production. Every time I watch Web Planet, I am totally amazed that the powers that were in the BBC at the time gave the green light to a story that simply could not be realized in any plausible way in 1965, let alone on the budget of Dr Who. The only comparison to Web Planet in terms of concept and ambition that I can think of is probably Avatar, which had, so I understand it, a somewhat larger budget. And a somewhat more conventional story.
We should also remember that Web Planet is still the record holder for the highest viewing figures a Dr Who has ever had (not counting 1979 when a strike on commercial TV stacked the deck somewhat in the Dr's favour. So it may look daft (and would have in 1965) but it is certainly unique.