So I've got a bit of a selfish reason for making this post aside from starting an autistic debate about the back end of RPGs again. I'm just playing around right now with learning inventory mechanics and learning them.
Every time I look at grid inventories, yes they're sometimes quite nice visually laid out and everything and it lets you sort stuff well as the player when they're coded properly. At the same time though from the player's perspective I have never really cared much about grid vs list I played the hell out of Skyrim and Fallout 4 and I actually quite enjoy the list inventories because you can quickly scroll down clicky click your way through stuff and you're done whereas with grids you're dragging and dropping things constantly and having to split items in a fairly tedious way.
My main point with this ramble is though thinking about inventory design does anybody here actually care that much about what the inventory screen looks like if it's clean and usable? I bring this up because if I choose to code a list over a grid in my projects that have inventory systems it's a remarkable difference in the work load, lists are definitely easier to deal with and take less code compared to complicated grid systems if all you want to do is let people pick up and drop stuff or equip things and there's not much else going on.
For extreme examples, think Skyrim vs Diablo 2 in terms of how they have their inventories. Been fed up of bloated RPG after bloated RPG being released so I'm going to play around with these ideas for the lulz while I think about my other work now my RL garden stuff is calming down.
It's not only about what it "looks like".
Like many mechanics in CRPGs, a grid is a proxy for a "realistic" backpack and carry simulation, without being too annoying. You can of course tweak what kind of grid you like to balance between realism and convenience, i.e. whether things stack, whether objects take up multiple "slots", whether objects have weight, etc. etc., and other comments pointed out the pros, but the fundamental idea is messing with objects and inventory management becomes an important part of the game. (and in that case you'd better get it right because it will be memorable to the player for good or bad)
Choosing a list simply means you don't want that mechanic in the game at all. The player is meant to find tons of objects in the world and figure out how to use them - not juggle objects and manage weight like a survival game. "All you want to do is let people pick up and drop stuff or equip things and there's not much else going on" as you say. Then The Inventory isn't part of role-playing at all but simply another status screen. (obviously you can still have things like weight limitations to add challenge)
So your choice depends on what best fits your game and what you/your target-audience likes.
Side note on inventory systems, another somewhat immersive idea was the one used in the 2008 Alone in the Dark remake, where you had to physically store items on your belt, and look around in 3D space to grab/replace items. Personally I think that kind of thing is way too limiting and annoying to work with, but it could fit some games and I wish designers tried uncommon ideas like that more often.
Grid systems are also handy for faster visual identification and sorting, but this only works when the kinds of items in the game (or their icons) are distinctive enough to not become a totally cluttered mess.
ARPG's are an example where I actually kind of hate grid systems. I've never honestly enjoyed trying to sort through 10 different melee weapons with different combinations of stats, almost constantly, throughout the entire game.
Somehow though, the list system in Borderlands was less of a pain. Probably because you could very quickly identify what you weren't going to want, based on details like the gun manufacturer, type of firearm, or tagline perks.
As much as I hate on Gearbox for going woke the clever thing that devs do is use colour ranking to quickly identify what's useful and what's not. Apex Legends has done this pretty well especially when the rankings are consistent whereas unfortunately a lot of RPGs aren't. The colour rankings also tend to appeal to the 5 year old in me because you immediately start looking for purple/red/gold items and start hoarding them :P
Same here, lol. Even more-so with legendaries and some of their lulzy (and sometimes informative) taglines. It's been a while since I've looked back on Borderlands and considered how well they did their itemization.
Sadly the Pre-sequel pretty much ruined the rest of the games for me by showing just how much of the game experience in that series depended on solidly planned scripted NPC-spawning events. And how much the questing satisfaction in it almost solely depended on humor, because from a gameplay perspective they were totally mundane fetch quests.