Isn't the fine tuning argument ad hoc?

[Tea Earl Grey Hot]

Theists argue that if the universe had not been created with the exact precise properties it has, then life would have never arisen. In other words, the chances that universe is the way it is is incredibly small. A universe that couldn't support life would've been far more likely. They of course conclude that there must of been some infinite and intelligent being (aka God) who purposely created a universe that would give arise to life.

All the questionable science besides, isn't this argument hopelessly ad hoc anyway? It postulates as a solution to a scientific problem something that hasn't been proven to exist nor do we have any reason to assume exists.

It's basically asking us to go "I don't know, therefore God did it."

I'd like to point out that it's remarkably hypocritical for theists to say that any of the proposed naturalistic explanations for the fine tuning of the universe such as the multiverse theory "isn't proven" or "isn't mainstream" when their solution is the ultimate of unscientific possibilities. Occam's razor I think compels one to select any naturalistic explanation other than "God did it" no matter how many problems it might have.