Website not looking good on IE 11 ever after applying prefixes

I was working on a website and mainly using display: flex for the layout.

I saw on the CanIuse.com website that IE 11 has partial support for Flex. So, I used the VSCode extension 'autoprefixer' to add vendor prefixes. But it still shows the broken layout on IE

This looks great on Chrome, Firefox, and Edge but not on IE.

I also put this website online temporarily so I can show it here

Website Link http://testsite.logicdeveloper.ca/

IE version 11.9

Any time of feedback will be appreciated.

Thanks