just because you pay the same does NOT give you the right access the same content as people who work and put forth effort in the game.
by you paying, all you do is give yourself the chance at attaining it. That's all.
And the effort required to access said content still requires the work, regardless of your subscription fee.
You and the LFR raider both have identical opportunities with your subscription fee. You can both clear LFR, Flex, Normal, or Heroic. That you choose to put in the extra work to reach the higher tiers and thus the higher rewards is not a relevant to subscription fee. If anything, you should be overjoyed that you're able to access more rewarding content for less money.