I miss Spitting Image - there seems to be as much material today as in Thatcher's day
I think there are two main reasons why we've never had a proper modern version of Spitting Image: firstly, it was hideously expensive to make (between 200 and 300 grand an episode - in the 80s!); and secondly those trying to remake it didn't really understand why it was popular in the first place.
There have been several attempts at reworking SI over the years, e.g. 2DTV, and the makers would always claim that they were "correcting the mistakes Spitting Image made", which seemed to translate into "drop the satire and concentrate on the jokes". Except that (1) they weren't all that funny; and (2) it was the political satire that defined SI the most. It was largely down to SI that you had playgrounds full of schoolkids who could name most of the Shadow Cabinet...