I say this as someone who is rank 140 and did near all the challenges that aren't broken (and even some that are) pre-nerf.
Pepperidge Farms sucks and this isn't 'real life'.
As much as snowflake kids can ruin lots of things, it's not childish to want balance, and handing powerful equipment to players simply because they play more is just stupid old-fashioned unbalanced poop.
It wasn't good in BF4 and it isn't good now.
It just creates a fake 'skill' (not skill, power) gap that lets experienced players noob stomp like griefing trolls.
Unlocks should give variety and flexibility as rewards not hand out raw power to give further advantage that experienced players don't need.
Crazy challenges for skins and other 'bragging rights' stuff? Sure. Go ahead. Crazy challenges that hands out power advantage? No. It's stupid design.
And no, none of that compensates for basic sense and tactics. That's not what balance is about though. It's about having a level playing field for all to have a chance to enjoy the game. It's not 'participation prizes' it's basic fairness way before prizes are handed out.