I like 'mobile first' design but I prefer 'mobile only' design.
A mobile design for an app or feature will usually scale up to fit a desktop just fine. Suboptimal but fine. It doesn't work in reverse though, desktop designed experiences that have been shuffled around to work on mobile are too often terrible.
'A better experience for desktop users' can be a feature request somewhere down the line when it becomes a real pain point for real people. I find there's rarely a good reason to make it part of an MVP or early milestone.