Why do futures trading fees feel so expensive?

Because fees are calculated based on the actual trade value, not the margin.
For example, if you use 1,000 U of margin to open a 10,000 U position, you pay a fee when you open it and again when you close it. (Trading fees are a necessary cost of trading.)
So what often drives fees up isn’t the fee rate itself, but large positions, frequent opening and closing, and more taker trades.

In short: leverage doesn’t directly increase the fee rate, but a larger trade value can significantly increase the fee amount.