To be fair, every game in the BG series (1, 2, and now 3) has had atrocious inventory management/UI. Inventory management in BG1/2 is like trying to fit a castle's worth of personal possessions into a shoebox apartment. In BG3 it's more akin to having a junk yard that occasionally randomizes object locations to search through.
Inventory space is always an issue in BG1, and especially BG2 when you are littered with well-designed, useful magical items. My character may have graduated beyond using Daystar or Ilbratha as my main weapon, but you betcha I'm keeping them around for the mirror image and sunray castings.
The containers introduced in SoA and TOB helps with the spacing, and there's a reason why some of the most popular BG2 mods are more containers and item stacks, but searching through them is even worst. Needing to open up and scroll through multiple bags of holding or scroll/potion/ammo cases to find the 1 item you actually need is NOT a good time.
By today's standards, the classic BG2 is missing a lot of things you'd expect in a UI - i.e. not being able to see how items affect your stats in the Inventory (i.e. damage, thac0), any form of item compare, etc. For all the questionable new content and mechanical changes the EE brought, they've actually improved on this quite a bit. At least there's a decently accurate damage calculator and Thac0 indicator ON the inventory screen now. Whereas before you had to manually switch over to the Records screen to see that.
Now after the Patch 7 update, BG3's biggest inventory sin continues to be how incredibly janky it feels to move items around, and the fact that it's not well designed to manage the amount of items you can accumulate. Also, it's multi-player-first design of inventories (most noticeable on things like the vendor interaction screen), really drags it down in a single player experience.
BG3 definitely has the most optional clutter of all the games - since any interactable object can be added to the inventory. This on its own isn't the worst thing in the world - the issue is the inventory control lacks any features and options to help you move around large amounts of objects easily. You accidentally press the "loot all" button a few times too many, and now your inventory has TONS of trash that you have to remove one-by-one. No way to select multiple items. Not easy way to remove from inventory in 1 click/action.
IMO, they really need to add the scroll, potion cases, etc from BG1/2 to BG3. Specific item type containers that helps the players keep organized - not just random bags you can toss any random thing into.
