I feel like the xp is fine personally. I get a level up and a half now with most full matches on the weapon I use.
I'll still say that the attachments level requirements should have been lowered and the cosmetic being high was fine, but instead they made cosmetic easier and left attachments. Kind of backward thinking on that.
Actually, I will say that there might be an issue with sniper and DMR speed simply because recon doesn't get a lot of additional points or XP from other actions that would also apply to the weapon. I think in previous titles you got more points/xp for longer range shots, maybe BF6 needs that as well.
Though if your complaint is that you play one match and your weapon doesn't go from 0 to 42,069 in that one match...