It's almost seems like stats got involved in development one day..."ok, we just need to find a way to stop 9 out of 10 shots" - it's effective but it has no upside. Like C1958 said, it's the lowest common denominator, it produces cookie cutter goaltenders... I just wish I was old enough to have seen the evolution of the position and understood how it came to be this way. It's hard to grasp when I just start watching a game from the 70's or whatever, there's no context to what I'm watching....
Well, perhaps I can help, as I came up playing through all 3 styles, Floppers, Stand-Up & Butterfly, whereby elements of all 3, based on the individuals strengths were taught, employed. I had 3 major Goalie Coaches as a kid, the first being Ed Chadwick, who despite his size, was absolutely a Flopper as a player, though as a Coach also a student of the position who understood & could convey/teach elements of Stand-Up & the Butterfly. He'd of course played in an earlier era (pre-slapshot) & was still playing when I knew him (albeit in the minors & Sr. by that time). So as his pupil, you'd take the best of his Flopper game along with elements of Stand-Up & BF. He'd studied Hall, youd be remiss & foolish not to have done so, borrowed from him (which we did, but only on dekes, scrambles in front when youd lost site of the puck, making yourself "big" because you didnt know where the shot was coming from if at all)..
Chadwicks instructions were followed by Plante, the man himself, who by this time had fully developed the Stand Up, playing the angles, economy of motion to a fine art & science. Again, as the student, youd take parts of his teachings & game, reject others that didnt work for you as an individual in-play, be it due to size & or physiological constraints, perhaps difference from a psychological perspective or whatever. Youd simply take bits & pieces from the Flopper to Stand Up to Halls' Butterfly, make them your own, unique, similar but "different". Jim Rutherford was another Coach, who only through force of will & hardwork ever made to the NHL. He'd been taught by Bower & others, those reservoirs of knowledge opened to another generation through Lil' Jimmy & so on. A couple of other Coaches as well, former Minor Pro players from the 40's & 50's who wouldve learned from the guys who played in the teens, 20's & 30's & so on.
Now, before I go on, its important to put the manner in which the game was being played at that time into perspective, which was basically "Laneway Hockey". Defenceman didnt join the rush or lead it much, Wingers played their Wings up & down rarely venturing beyond maybe 15' out from the boards. Think of a tabletop hockey board. Your Defence can only be moved to the opposing sides Blue Line on a straight groove, your Forwards also on straight lanes with an arc into the left or right corner, your Centre stopping in front of the net in between the faceoff circle hashmarks. No East-West or lateral movement allowed. With Orr's arrival coinciding with rapid over-expansion, the WHA, then the 72 Summit Series, the way the game was played over the next decade of the 70's had changed forever, goaltending playing catchup until really the mid to late 80's but through the late 60's to about 87 you could move your Goalie not only East West but now so too North South, playing the angles.
By the mid to late 80's, that tabletop hockey board now featured grooves for the forwards & defenceman to play all over the surface in constant cycles, and if you wanted to beat them, Left Wing Lock & Neutral Zone Traps the only way to do so, which in combination with the composite sticks (everyone now has a deadly shot, not everyone accurate but none the less, deadly), the game played in cycles by bigger, faster & stronger players, absolutely no way you could play Stand Up exclusively with elements of Flopper & BF included in your tool box. Kirk McClean was probably the last of that kind, though guys like Brodeur & to a lesser extent Thomas & Smith in Phoenix do employ elements of it when required. On the whole however, Goaltenders are taught to "block" as opposed to "save", size critical, and were back to the future, Ed Chadwicks era & earlier, whereby the goalie on your tabletop hockey board no longer is capable of moving out, North South. They still love it, enjoy it & playing the position just as much if not more in some cases than those who came earlier, but that "old bag of tricks", long gone.