In a word: RNG.
There is challenging RNG, and there is punishing RNG. Punishing RNG without any player input leaves the victim feeling cheated, and TFT is full of this. I feel cheated often within the first 3 rounds of a TFT game due to drops. Items bring builds together, they let players choose where to weight their strength. Gold lets you put a board together but without the items it is neither your unique board nor a winning board. So if you are unlucky enough to get gold in the first 3 rounds, you may feel cheated for the rest of the game. This is especially pronounced because you know there is no assurance that you will recoup the missed items in later monster rounds. AND the gold rewards for getting that instead of items is 4/5/6 in later rounds. Items should have a uniform value for gold and the number of item drops should be uniform across players (but maybe not matches). A lot of people have mentioned that item selection from 3 would solve this, but I disagree, Items have a lot more variety in uses than other games like this, and so getting one item you didnt plan for isn't going to ruin a build, it just forces lateral thinking. I think the champion selection RNG is fairly balanced already, but items are currently in bulls**t state.
Two additional notes. First, remove player collision. It can ruin the wheel because player against player collision gets glitchy and can screw pathing over, you can even block people from getting to their desired picks, or slow them down at least. And second, consider how to make board pathing/targeting smarter, occasionally melee champions will run around 6 hexes to get to the target they chose rather than move 2-3 hexes the other way to a new target. Again, low player agency..and it just feels like "I lost this round because I was unlucky" not because an input mistake was made.