> Once you get to the endgame it's pointless, and people basically blaze through the base game on purpose. And once you get there it really is no more than a slot machine that caters to people with serious gambling addictions.

Feels like you're missing the point of end-game players. It's not the slot machine. It's pushing further and further into end-game content. It's a race to see who can dive deeper into dungeons and what builds are necessary to push to the true "end game". Diablo, the campaign, is and has always been trivially easy. Super high levels of these dungeons stack up so many resistance penalties and the level difference adds so much damage reduction (for enemies) and increase (for you) that it becomes much more of a skill based game. This is what I play these games for. Not the campaign that you can sleep through.

For my wife, the game ends when we kill the big baddie together on normal difficulties. For me that's when the content just starts getting interesting. There is a lot of grinding involved, but you're having to pay so much more attention to what abilities / upgrades / paragon selections you make none of which are important at all for the main campaign.