The Substance is just too up it's own ass with cringe feminist shit that it really hurts the movie to me.
Tbh, the movie is only as feminist as you want it to be. For every "the patriarchy made her do it!" you can also raise a counter argument.
Fred loved her despite being old and past her prime, he valued her for her, not for her looks, he was someone she could have settled down with but because she had a huge ego she thought he was a gross nerd and rejected him until she was desperate for validation, before standing him up. She's clearly the bad guy here no matter which way you look at it.
Harvey is gross and meant to be gross, but nothing he does is because of personal prejudice, bussiness is bussiness at the end of the day and his sole motivation is money and nothing else. In fact he was perfectly understanding on her sick mother and let her chose the schedule with no issues. He didn't force her to work on off weeks. He reworked the entire show around her demand. Harvey didn't force her to steal time from her other self.
The first time she steals time it isn't because of work or anything, its because she wants to get wasted with and fuck a bad boy she met in a bar.
At the end of the day she is the source of every single one of her problems. She got greedy and stole time, she had a huge ego and rejected nice men she thought were "below her", she refused to take responsibility for the fact that she is one and treated her other self as a stranger and refused admit that the rules also applied to her when she went on the 3 month bender.
At the end of the day, she was a single woman during her 50 with no skills other than shaking her ass on camera, no family, no connections, no other abilities. She could literally vanish for weeks at a time and nobody cared.
She was gifted with beauty in her prime that put her ontop of the world that she procceded to completely waste drinking and fucking, making zero plans or contingencies for the future. The substance gave her a miraculous second chance to try again, and then she completely wasted that second chance too because she is a selfish egomaniac that wants everything NOW NOW NOW.
And honestly, the reading of the movie as the innevitable downfall of a narcissist is way more compelling as a tragedy narrative than "The patriarchy made her do it".