So there is no reason to remove the time gate on stories because they already have to stick around for the gear. You are also assuming that the same people that do the story always do raids, M+, or PvP. You keep creating different restrictions and play styles based on the argument you are making.
Do you honestly think that once a person gets their "best in slot" they never log on again until the next tier? They aren't going to PvP? M+, Raid, or do rep's and quests for fun?
You literally said they are not though. Because the only thing that keeps them doing that multiplayer content is a time gate. And that if you remove that time gate they would stop doing that multiplayer content as soon as possible. That means they are interested in gear and not the content they are forced to do for the gear.People that raid are interested in multiplayer content, because raiding is multiplayer content.