For those who don't think players will laser focus the quickest and most optimal route well... I hope you get to keep your innocence. The reality of it is that optimal and speed is the name of the game these days. Let's just take a look over to WoW with it's M+ content. Not only is it timed to make it harder (which encourages fast routes) but tanks are practically required to be running an Addon that calculates the most optimal route in higher keys. Unfortunately, if SE were to create harder dungeons stuff like this would start cropping up here. Maybe not in the form of addons, but this time rather guides and required pathing.

As far the harking back to the days of ARR Hard modes... we remember these very differently. Trying to get a group to complete Arum Vale and Pharos Sirius Hard pre nerf was... good luck. More often than not you'd go through at least three tanks in Arum Vale before one stuck it out, and getting a group to finish Pharos Sirius was hell. I don't know about you, but for me the rewards would have to justify the pain one would be required to go through to finish. While such an experience can be fun with friends, the moment you toss in a pug it is game over.