I'm talking specifically about picking up weapons. It's not a slow process.
You're missing the point entirely. Sorry for not being clear enough.
The core issue is gameplay, not realism. The second issue is creating a cohesive world. The world doesn't have to be real, it could be completely fantasy-like. It just has to be consistent.
The rest of this world Kojima has created has gotten to a point where some things that he was able to get away with in previous titles don't jive with the current world he has created. More importantly, there are some great gameplay implications if Snake has to pick up weapons. He can't simply run and shoot at baddies and then run over their guns to pick them up. Another situation is where he is holding a player hostage and the player drops his weapon in front of himself. So while Snake is pointing the gun at him with one hand, he could pick up the gun with the other, giving the baddie an opportunity to attack you while you do that. It would make the gameplay interesting, don't you think?
There's so much polish in this game in other areas, I don't see why people would be averse to this idea. I mean, when Snake runs over bodies on the ground, it slows him down as he tries not to trip over their bodies. Sure, it slows down the "fast" gameplay, but it makes the world even more immersive. Such a thing did not exist in MGS...but Kojima added it over the iterations. Again, I don't see why people would be averse to what I'm suggesting. And again, I'm not asking for a complete overhaul...I'm not asking for the sound fx for your inventory to be taken out, or for the inventory management to be taken out itself because it's unrealistic. I'm just asking for the same sort of polish Kojima is known for, to be applied to something that could affect gameplay in a positive manner, with the picking up of weapons. And again, I don't care whether it is in the final game or not, I'm just saying it sticks out like a sore thumb, as everything else is an another level in terms of immersiveness.