If you're stumbling on this in late 2024, recent Office 365 update may have been rolled out at your workplace. There is no way to disable this feature. While I do understand it can some benefit people, this was awful to set as default with no option to restore original Formula Bar Font. I deal with data sets where character spacing matters/may be wrong, and this view is screwing with my head big time. It's like wearing the wrong pair of sight glasses, or not needing glasses and putting someone else's on.
The best you can do is go to File>Options>General and try using Calabri font. I hate Windows 11 Start Menu in the middle, but at least we have the option to change it back to legacy. Don't like the Windows 11 right click and having to go to more options? We have the option to go back to legacy view. Don't like this change in Excel? Well we don't have the option to go back to legacy, absolutely awful decision here.