jmartkdr2
Hero
You could use magic items to pick up the slack, basically make levels a small thing and magic items the point of adventuring - this makes it easy to tie rewards to the pace of the game, because loot usually happens at the bottom of the dungeon.I've been pondering this a lot over the past weeks, and I think it's that getting new toys every level is something that creates a sense of accomplishment and progress. It functions both as lure and a reward to encourage players to keep playing and have something to look forward to that they can see getting closer.
When this element of the game disappears and all you get from new levels is increased passive numbers, then you need something else to take its place as an incentive that goes beyond finishing the one thing the players are currently working on.
For a campaign that focuses on shorter delves into smaller ruins in a larger environment, I think each dungeon should make the players feel that they discovered more pieces to help creating the greater picture, but also that they are still missing many more pieces that will make things even clearer, that are still to be found somewhere out there. This is a campaign and adventure element that exists completely separate from the mechanical parts.
But to do this you need to not use 5e's assumptions about the role magic items play: they must be seen as a core part of the experience and the main way characters grow, not an optional nice-to-have that shouldn't really change the balance of the game.