I understand the burnoit that comes with this style of game, but if you think about what you just said your point kind of falls flat. (Won't get into the "you must have been a RMAH player" argument.). When you first got into Inferno back in classic there's no way you had found the gear to have went all the way through the Acts up to and defeating Diablo on that first entry. You would have had to grinded to find the gear needed to get thru the lvl and beat Diablo, which most likely did not come super quickly. Then when you finally rounded up the gear, you made it to the last boss and defeat him, which was a great feeling of accomplishment. That's the way many people feel right now when it comes to pushing up higher and higher into greater rifts....search for getter gear/builds to go further, rinse repeat... Yes it is obviously grindy, but so was your conquest to beat Inferno Diablo...
At least you probably spent a lot of time in the game that it was worth the $$ you paid. Again, probably more so than other games that can be beaten in 10 hours. Spending $60 on a game I beat that quickly, without replayability, sucksssss in my opinion. Yes WoW gets more expansions and stuff but those also cost $40+ each time....at least D3 gets some new stuff free of charge now and again...