IMO - If this game is to stay relevant - the gameplay needs a massive overhaul

[Einheri]

What is horizontal progression? I keep seeing the term thrown around and each person uses it to fit their own desires.

Gw2 is basically all horizontal. You get max level then a set of exotics then grind and grind for glamour's. They didn't even raise the level cap for the xpac.

In ff14 you constantly replace gear as part of your grind. Then you glamour over it.

I do think they could scale more content. It would have to be purely optional as people already complain they can't face roll scaled content, while others complain everything is faceroll.

Like expert roulettes could scale all dungeons (at least the last 6) to be challenging. In this way you see more then two dungeons in your roulette and people will be happy they can't face roll. If you want a face roll run it on regular.