[a_cardboard_box]

Independence of irrelevant alternatives doesn't seem like a desirable property to me. It suggests that someone ranking a candidate 2nd vs 100th does not tell you anything about how much they prefer their 1st choice to that candidate.

Suppose 50% of people rank Alice first, Bob 100th, and the other 50% rank Bob first, Alice 2nd. A voting system with independence of irrelevant alternatives would have to rank Alice and Bob equally (or at least it would have to rank them the same way as it would if they were the only candidates, with 50% preferring each one). But Alice is probably the better candidate - she's in everyone's top 2. The extra candidates give you information about Alice and Bob: they show that preferences for Bob are weak, and preferences for Alice are strong.

[Maxatar]

I think I get the jist of your post and why IIA might seem objectionable, but your example does not reflect IIA and the claim that any voting system that satisfies IIA must rank Alice and Bob equally is not true.

The score voting system satisfies IIA and can result in a situation where 50% of votes assign their highest score to Alice and lowest score to Bob, and 50% of voters assign their highest score to Bob and their second highest score to Alice. Alice would end up winning the election and there is no opportunity for the introduction of a new candidate who could act as a spoiler for Alice.

Arrow's impossibility theorem does not apply to score voting since the theorem only applies to voting systems where you rank your choices, it does not apply to systems where you rate your choices.

https://en.wikipedia.org/wiki/Score_voting