No mater how much you want to try and shy away from common practice, loot is at the end of the day exactly that. Either something you use or money. You want it as a part of a gun, it has a use. It's an armor better than yours? It has a use. When it doesn't has a use then it has a monetary value so that if useful stuff doesn't drops, you buy it.
That's your perspective yes and it may be common practice in some games but far from all. I listed numerous examples of how loot is used differently, to different ends.
Everything in underrail is useful! can you tell me of something that you pickup that has no use? Even if you can I'm sure it's something incredibly rare. Everything has a use. Society has collapsed, the few survivors life in the metro and bunker dug and fortified inside the earth. Resources are scarse, do you think people who scavnge for stuff wouldn't horde and sell everything? If they found a place with stuff they'd pick it clean! Eveything has a value!
But does it have value to you? This is where the itemization becomes interesting to me. The carry weight is not in the game for the fun of it. It's to encourage you to think long about what kind of stuff you want to fill your inventory with. If you use and craft crossbows and grenades, you will pick up crossbow parts and chemicals above anything else, because it's the skill that keeps you alive. If you find a random piece of loot that doesn't have actual value to your character, what item will you compromise to pick it up? Should you pick it up or hold on to your more valuable items instead?
Obviously people can't carry a train on their back nor do the merchants really have unlimited amounts of money. But this is where gammy sense has to overcome real sense and if needed you can justify it very very easily. You can have some sort of backapack that can magicly (or tecnologicaly) store whatever you put inside and with no weight associated to it. Merchants will never buy you anything at all, each town has a storage which buy anything and everything, they have quite literally tons of money. Merchants only buy things from storage to sell so the storage just has lots of money because merchants need to aquire stuff from them. Easy to justify things if you really want but above all, it stands to reason that gammy sense has to prevail over real sense in some parts to make things work.
It's not like the itemization and trading doesn't work. It does, it's just not tailored to your style of play.
Also it's wrong to compare this to ARPGs (or hack and slash games as I call it). In ARPGs you are put in a situation that it's neither profitable nor timely to get every piece of loot. White loot won't even pay for a scroll and the time lost in going to town every 10 seconds would make playing the game pointless... Even then there are ARPGs that do that right. Look at Sacred 2 and you have a perfect example. You have a huge inventory and you can instantly sell from the inventory at a smaller margin but the value of white items are not high so the loss is insignificant, meanwhile you keep getting every piece of loot and selling and not stop playing thus not breaking game immersion. Do they bother explaining how you can do that? No, why would they? It's a thing meant to keep you playing and have fun, it only has to make gammy sense, not real sense... But going back to proper RPGs which use a turn based system you are supposed to pick up everything. Take fallout 2 as an example. Did you leave any loot behind? I know I didn't. I know I sold everything I got my hands on! If there was too much loot I'd store everything I couldn't carry in a closet near the exit and make trips back and forth. this is where the game could have used a little bit of a hand. No carry limits would make those parts less boring and keep you constantly engaged on the fun. Similarly there was no unlimited amount of money on merchants but in any given place they could always buy all I had and if not I'd just start getting stimpacks as money replacements since you use a lot of them anyway. There was no limit or this type only of items that they bought from you and again, if they had unlimited money, it would only have made it better because again, it would have less of boring trading time and more time engaged in playing the actual game.
I wasn't comparing the games per se but their respective view on what loot is and its value. Loot in Underrail is clearly not meant to picked up at all times, if you want to do that, you need to make sacrifices, just like you mentioned you did in Fallout 2. Like most of the loot in The Elder Scrolls is just decoration and world building and how items give you lore in Dark souls, they have different reasons to exist and Underrail excercise its itemization to encourage scavenging and if you embrace that, it's a damn fine itemization system. If you don't, or if you can't for some reason, then it's probably not the very best system, but that goes for everything.
I understand that Styg has different views for his game and I do respect that he wants to do some things differently. But in these areas I feel it's an exercice in futility. People don't like these things. People don't like to have their time wasted or feel like they are being cheated out of their money. He could have dealt with it the same way he dealt with the oddity system. Make it an option, not an obligation... At any rate it's very likely people will mod these exact things I'm talking about. It might take a long time or it might come up quickly. But it's sure to be expected to happen either way because most people won't like it as it is. The same will go for the crafting, I'm sure someone will mod it to make crafting useful from the very start but that's a whole new can of worms.
I agree that making it an option would be cool but I think I've answered this very exact thing a few months back. Can't seem to find it right now though.
What I mean is. If it's already well known that mechanics which make people feel cheated of their stuff or make people feel like it's wasting their time is pretty much widely disliked. Why go so hard on making sure the game has it? Why give the moders the credit for making a game good instead of the developers taking the credit for having made a good game? Again, so long as there is options and you can chose whether or you want those mechanics or not, then there is no problem.
I haven't actually seen a lot of dislike for the itemization. I can count on my fingers the amount of times someone have complained about it, most people actually like how the itemization works otherwise it would be a hot topic frequently but it really isn't. And I'm pretty sure Stygian won't expect their audience to "fix" their game for them, and even if they do it's to satisfy a relatively small portion of their audience, given the low amounts of complaints on the area.
Of course you can say those can be added last and you'd be right, but then how much testing is the game going to have with those options? Sure the early access is mostly a way to gain revenue to help funding the game but still, if you can use feedback to improve the game then it should be used in all aspects of the game.
You have given your feedback, time and time again. And people have listened, and replied. Styg have listened, and replied. Though not in your favour because he have other plans but he have indeed listened. I've given my rather less favourable opinion on the leveling system but I don't expect him to change it if he have better plans, I've given my feedback and that's enough. It's fine to throw your opinion out there, if it sticks, cool! if it doesn't then I don't see the point in nagging.