That's the problem. Freely obtained stuff isn't grinding. It's instant gratification. This is at the expense of actual gameplay.
Cosmetics can be churned out way faster than actual gameplay. Plus the people who make the mounts aren't the same people who make the warzones and operations.
If you consider cosmetics themselves to be gameplay, its about a year and a half late to be bringing up that objection. When the CM was first brought up it was made clear that the CM would sell cosmetics, and subscribers would keep(and hopefully gain more of) content. There wasn't substantial complaint at the time(people were rather more concerned about how f2p would affect things like lag), so that's how things went ahead. As long as its cosmetics being sold on the CM, Bioware's kept true to the stance they've had on it since it was announced.