Except, the spell uses "you" when discussing how the spell works in general.
Which in every instance of every spell and every class ability is the person who used or cast the spell. There needs to be very exacting language in the spell to override that. I think someone upthread showed one instance of that.
So if the spell is cast upon other targets, they become the "you" in how the spell works.
They only benefit from the effect in this case, etherealness and anything that results from that. They do not get to dismiss the spell of the caster. There is no language to allow individual dismissal, so the spell cannot do it without a house rule to alter the spell. If you allow anyone to dismiss it, they would be dismissing it for the entire group including the caster, which is also ridiculous.
"You" is the caster.
For example: the spell states "you can move in any direction." Clearly, if the spell is only affecting the caster, the "you" is the caster. But if the spell is cast on others, the "you" is anybody affected. If the "you" in the spell only refers to the caster, then only the caster would be able to move in any direction, not any of the others affected.
That's not the spell. That's the ethereal plane. They are there, so they can move there. The spell is just trying to avoid having to go to the DMG as much as possible.
The spell transports them to the ethereal until it ends which is 8 hours or when the caster dismisses it. And again, unless there is explicit writing to allow someone else to end the caster's spell, they can't do it.
The heart of my question lies in this sentence: "You remain in the Border Ethereal for the duration or until you use your action to dismiss the spell."
Obviously, "you" in entire spell description applies to anybody affected by the spell, except possibly the one sentence above.
If you look at the spell, the entire thing is written for a solo person, the caster. Then at the end it allows the caster to target other creatures and it specifically says(including you), indicating that the uses of you are still the caster. The movement section of the spell is just ethereal movement.
Other than simply bad wording, why would the "you" in that one sentence only apply to the caster, but every other "you" in the description apply to anybody affected?
Spells have never and in 5e also do not work in a way that allows anyone who is not the caster to dismiss them. You need explicit language for specific to beat general, and that language is not present. Absent that language, the "you" dealing with the casting and dismissal has to be the caster.
It's not the first time WotC has used the same word to indicate two different people. You'd think you would know who is being talked about when it says Player, but the DMG says the DM is also a player. So the game has Player and player. In this spell there is You and you. Those uses of "you" dealing with how the spell is cast and ends are "You." Those dealing with individual movement on the ethereal would be "you."