Yea that’s what I’m not sure about, how retail handles the multiple lockouts thing. Like, I can go do the same raid multiple times per week, I just can only get loot from a boss once per week. Can you confirm that the data you’re looking at filters that out?
I did some googling and found several sites claiming to say what the player count was for 2025 and they ranged from 1m to 5m.

The bottom line here though is that I’m not going to disagree with you that retail currently makes up the bulk of the player count. That doesn’t mean that the player base Vanilla appeals to is insignificant, or is never present.
I’m not sure if you wrote what you meant to wrote or we have differing understandings of what horizontal progression means.
I’m not advocating for a long chain of gear progression ticks on a list that a player has to go through in order to be relevant. I’m suggesting that each tier be be relatively self-drive for localized progression and that the global power level of gear outside those tiers (ie, open world, pvp, dungeons, etc…) be generally similar.
This means a player could join the game in P14, get decked out in pre-bis dungeon gear, and be ready to tackle early bosses in the new raid just the same as they could MC. They gear up in that raid tier and their global power catches up within that season, though they may still want to chase several BiS items available in other raids to truly min/max their build. When P15 comes out, maybe some of that gear’s power isn’t applicable to the new raid and has to be replaced within that raids progression system, but their overall power outside that tier (and relative to the tier they obtained it in) remains constant.
Or something to that effect…
No, that’s not what I’m advocating here. There would still be expectation that you’d have to progress in some way (gear, but not always) within that tier… just that your global power isn’t reset every tier and you can go back and do all other tiers at roughly the same power level.
Also please keep in mind that ultimately, I’m not saying I have the solution. I’m inviting conversation and speculation.
GOAL: Keep all content tiers in Classic+ relevant.
SOLUTION: <please submit your thoughts>