We're moving things around. There is only so much storage for attributes and such. Would you rather have a "bike seat" that does nothing really, or be able to add armor to that bolt on slot? The initial release we just sort of filled those slots with stupid ♥♥♥♥ and nerfed things to simualate growth. Yes gun parts are probably going bye bye to make room for real mods. Nobody ever liked tearing guns down and combining ♥♥♥♥ just to un-nerf its intended use. This is just another sharp stick, I promise you you will not miss. The real fun is crafting something decent, then upgrading it to something badass. That is the overarching goal here.
The good news? Player gun crafting. Then you seek out legendary "parts" to add to them, etc. Those slots wasted on barrels handgrips, etc can be used for diablo like mod slots.
I mean nobody gets excited about finding an old handgrip in a box. But finding a full firearm that can be used is much more useful. Instead of tearing it down, repairing each part, combining a few parts, etc (all tedium), you would combine/repair two whole guns into one. Its the same mechanic without the micro assembly nonsense. That part would be used to install mods, which is way more rewarding. Real mods that are coded in to do cool ♥♥♥♥, not just simple un-nerfs to get a useless gun barely usable.
You can disagree, but all it is, is people getting used to old fluff that we used to fill out an incomplete system. The finished system with mods and legendary weapons will be way cooler. But its still in its conceptual stage at this point, but whatever we decide on for guns is going to be the same system for vehicles.