My philosophy regarding voting and the shop is this: We want players to vote, so we give them a reward for voting (coins). If coins are worth nothing (because there are so few shop items, or someone already has all the items or the items are not appealing) then players don't care and they won't vote. The reality is that most players won't vote out of the kindness of their heart. By player standards, it's not particularly easy (below ten seconds + there are several voting links) and if the reward is not interesting, they don't care.
But I agree with StevenNL2000 that we need a distinction between a shop item and an everybody feature. Each type of feature available in the shop should be accessible to all players. The shop should be used to make "extra" cosmetics available. For example, the lightning rod is a blaze rod that can summon lightning with a cooldown. All players can give themselves a blaze rod, and all players can execute the command to summon a lightning bolt (as long as they don't spam it - equivalent to the timer cooldown on the shop item). Player particles were also brought up, so I'll use them as another example. What if we gave all players the command to access particle type A and B, and particle formation C and D - possibly rotating which types are available to all players each week to keep it fresh - but put particle type X, Y, and Z, etc in the shop for people to buy. That way, all players have access to some particles that get swapped around, but still leaving room to have reasonable cosmetics in the shop as an incentive for voting.