The change in 1995 had a big impact because the WTS depends on a sense of urgency to push its message and control the rank and file. In the years leading up to 1975, the ranks grew quickly because people will hedge their bets 'just in case.' They had long been using the "1914 generation" teaching to show the urgency of the times, even in 1975 (the 1914 generation would have been in its 60s or 70s by then).
They designed that famous cover in 1984 talking about that generation, which would have been 70+ by then. By 1995 the sense of urgency would have been critical; the 1914 generation was now in its 80s and 90s. It is hard to see the "change in understanding" as anything other than a convenience; as a way to get rid of a growing problem. It should also be no surprise that many left around this time, because it's hard to avoid the feeling that you were being pranked.
But the loss of urgency is a problem. That's why they decided to revive the "this generation" teaching and came up with the "overlapping generations" abomination. I'd really love to know who decided that it was a good idea to do that. I wonder how many JWs who held on after 1995 saw this and realized that they were following a bunch of clowns.