While not trying to be rude here, but if you can't take a comment on a forum, perhaps you shouldn't post in the first place. It was just an honest opinion, whether you agree or not it's your own chosing of course, but I don't see how debating something is ever negative... You said yourself you don't like merchants not buying everything, I discorded on the point of them buying at 10% the value cause the value is so low that it's just not worth the trouble of getting everything, going back and forth repetitively to sell what's on the inventory. It's busy work, it feels much like an MMO telling you to do fetch quests.
Now you give a real life example but here's the thing. This is not real life, it is a game. Does it makes sense that you kill an enemy and you level up and suddenly you know how to do something new? Of course not, that's not how it works in real life. But, it makes sense in a game!
Having multiple sellers, each one selling a particular type of item is not because it makes sense. You could put just a seller and everything is bought to him, the reason why it isn't so is because it becomes a major pain in ass to scroll through everything, multiple sellers are just tabs to separate item types. It also gives a sense that yeah, it's how it would work in a real world so it gives some immersion to the game, but ultimatly, it's all about having less cluter.
As for selling, let's go by parts here. Let's say for example they just buy every single piece of equipment so long as it's compactible (no limits to number). Would it make sense in a real world perspective? Yes. Is it necessary in a game? No. It just makes busy work going in between all of them to sell your stuff. If you could just go to one, sell everything at the same price and go back to exploring the world and doing the things which are fun in the game, wouldn't that craft a better experience?
As for selling limits what does this means? Well it means that a lot of your loot is going to just turn useless. The major objective of exploring is finding new stuff and conquer new challenges, however if all of those challenges give you nothing it makes the experience void. I personally would find myself wondering, why did i go through all the trouble of coming here, kill everything that moved, search every corner of this part of the map and get nothing for my efforths? This is the risk/reward factor, although you could add time to it as well since exploration does takes it's time... So if you expect to be rewarded for exploring as it is the major driving force of it, then the merchants not buying everything means that exploring is not rewarding you because you are not getting anything out of your explorarion... If you go through the main storyline only, you are still going to get way more loot than you can sell and yes, you probably are not going to run out of money,so exploring which will yield more loot is just going to be yielding nothing. Maybe XP but XP alone is hardly a driving force. If you need to go out of your way to grind XP then the feel is that the game isn't well paced.
In fact if there is a huge worry about it looking as real as possible then just slightly tweek the system into a way that would fit in the world and makes a high degree of sense.
You could for example have merchants only sell you stuff. They don't buy absolutly anything from you. Now because we're talking about a post apocaliptic world, resources are scarse so no matter what it is, it's always in demand, heck if you have 300 pelts. They are still in high demand and useful... Why? Because putting things into perspective, there are several cities so even if you don't need as much, that's ok because background wise all of that stuff can be traded in between cities to cover for stuff they are lacking. Thus demand never faulters... Now how do you sell stuff then? Well you have a storehouse which buys everything and always at the same price (because demand does not goes away). You sell everything there and go to the merchants to buy whatever you want... Background wise the storehouse is responsible for keeping the stores supplied and bartering with other cities for necessary goods... It is so incredibly easy to just make a system that works. You can sell everything and at the same location. You keep the merchants so each sells it's own type of stuff, thus you remove cluter of having it all in one guy.
Last but not least. I really like this game. I bought it back when there was no weight limits and merchants bought everything and you know what I thought back then? Best looking game ever since fallout 2. I was genuinely happy for no carry limits and merchants buying everything. It kept me away from wasting time going back and forth to sell my stuff. It kept me immersed because I didn't need to stop half way through a map just to unload stuff or going between several merchants and still have loads of loot left at the end of it... All this immersion is now lost to me and worse than that, it just makes the game feel like it doesn't respects your time because the time you are putting into it is just being thrown away by the lack of rewards.