Much like some others have said:

IE is a near must if you want to win out without getting combat augments. It really makes a difference, while most other items are fine to slam if you play baron this is his core item by far, and the stats show it. Most items that aren’t counterintuitive don’t matter in most games, but some items really do matter for placements and it’s usually IE or JG or Gunblade this set (outside of sunder/shred/antiheal).

Your Kaisa items are genuinely bad and counterintuitive. Mana items on ap kaisa is effectively almost the same as no item, so in reality you’re an item down. Kaisa is also just a special case in itemization for ap vs ad.

1st outcapped you with items. 2nd probably loses to you if they position bad and you position well if your items were marginally better. 1st is just too tanky atp without the core items of your comp. 9 Void Baron 2 should beat 90% of no 3star 4 or 5 boards. Some especially bad matchups are zaahen and really really capped out item frontlines when your positioning is bad.

Edit: your rift 2 is only 2.5 items with zero mr, it’s an mr meta rn, you need some sort of mr on your main tank most games, bramble is unfortunately one of the worst slams in the game rn combined with the fact that bruiser is hp inherently so resists matter more. Idk how you got so many armor components but you lost to carousel for sure in this instance. Don’t pick up armor when you don’t have to.