My biggest issue with Mac-only shops is that almost nobody actually deploys to Mac. The majority of Mac-only firms I've worked at deploy to x86 Linux and develop in a VM on their Macbook (even pre-M1). Unless your business is writing Mac-native apps, MacOS is probably going to be a second-class deployment platform for you.
Even in an ideal scenario where your app already works on ARM, you will be dealing with OS-specific quirks unless your production machine runs MacOS.
Even in an ideal scenario where your app already works on ARM, you will be dealing with OS-specific quirks unless your production machine runs MacOS.