Designers only looking at their sites on their MacBook Pros is exactly what produces these pretty but unreadable websites.
Microsoft's refusal, or inability, to release a version of Edge (or even a port of an earlier IE) for macOS exacerbates this situation.
I virtualize Windows on my MacBook for IE/Edge testing of my designs and code, but it requires a workflow and context shifting that I'd perfer I didn't have to do.
Edit: s/I.E./IE
At least Microsoft has the good grace to put up free VMs for browser testing - https://developer.microsoft.com/en-us/microsoft-edge/tools/v...
The only way for me to avoid using the Macintosh OS or having to buy a Mac is to switch careers or specialize.
Thankfully, cross-platform kits such as Cordova and React-Native let me use my preferred OS for development most of the time!