I completely agree with you.
I came back to the game last weekend to try out the new patch after not playing since the launch of season 2. I read weapon XP has received further tuning and other XP gains now count towards the used weapon.
I'm sad to say the XP rate is still far to slow. I am not the best player, I average around 25-30 kills per game of breakthrough and I have only a few hours per week to play. At this rate it will take me months to unlock attachments for a variety of good weapons.
I would love to try new guns and builds but the grind completely puts me off and doesn’t make me want to play as it is not rewarding.
The only time the weapon XP has felt right has been on double XP weekends.