It does exists. Just because last 2 DLC (or 3?) you still use same ships. And you still can use basic E modules and do things. On vertical progression each new tier trashes all content before, makes it obsolete. WoW/SWTOR/many more are bright example of vertical scale. New DLC = trash all, go try new raid to get best new. Repeat once a year.
It's not about being able to use the same things as new players but better. It's your argument that there exists a scale of being "better" at the game for these roles. Horizontal scale requires that there is a measurable and meaningful difference between player skill and reward even though the task is the same. That doesn't exist in Elite Dangerous. Newbs can rake in the most credits right off the bat effectively and no amount of player skill will net you signficantly better incomes as a veteran player. Whether it's exploring, trading, mining or anything else other than tasks that require engineered/guardian unlocks. There's no scale there, so horizontal scaling doesn't exist.
How would you separate the veteran "skill" from the newb in the existing roles? The developers originally set things up so that only players who knew how the bgs worked and explored around to create a list of stations and what they sold and bought and managed those different kinds of info would be able to take advantage of them the best. But then they created the 3rd party api and made it stupid simple for crowd sourced data mining .. circumventing your horizontal scale for trading and mining.
Exploring has absolutely zero scale between a newb and veteran and no means of creating a difference currently even without third party tools.
Combat farming like i said, has maybe a couple months at most difference.
What I'm talking about is not trashing old and getting new stuff. I'm talking about making expensive ships expensive to operate but not necessarily required to play the game or even do the more complicated / riskier tasks (they'd mostly be for showing off). Then create these more complicated / riskier tasks to fund those expensive ships in a way that doesn't require huge amounts of time like trying to fund them off the beginner tasks (current game mechanics) would. There's no infinite arms race going on there like you described.