Why wouldn't you want an expert to run the economy is such trying times?

Because this so-called expert is a danger to the the common Argentine. His way of "fixing" the economy is by growing inequality, privatizing key government duties and destroying unions.

I personally disagree with him on many points, such as:

he has called for the elimination or merging of major ministries such as the Ministry of Education, the Ministry of Social Development, the Ministry of Women, Genders and Diversity, and the Ministry of Health.

Milei articulates a critical view of the role of the state in economic matters, calling it "the greatest enemy of wealth"

Milei wants to privatize public health care providers

Milei has expressed support for legalizing organ trade

Also, he is president of the country, not just the economy. I totally disagree with him on points like:

A supporter of law-and-order politics, Milei endorses the unrestricted ownership of firearms

Milei opposes both abortion and euthanasia ... Milei holds that abortion is morally indefensible, even in cases of rape

He intends to eliminate the law that makes comprehensive sex education (CSE) in schools mandatory, which he has linked to brainwashing, and said that students are "hostages of a system of state indoctrination"

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

regarding your comment:

So let me hear it. What would you do to so wonderfully fix the economy that an expert is getting all wrong?

This is a fallacy. It is of course not necessary to know the right answer in order to know that another answer is wrong. I might not know what 483 × 749 is, but I know it's not 10. Or 100. Or 1000.