The 13.3" screen size Apple uses is shorter overall than my 12" iBook from 20 years ago(meaning, if you play a 4:3 video on it, the iBook's screen is technically larger). That to me is too little. Too small to be used as a main machine. The Retina switch helped, as the highest "scaled" resolution is about the minimum for extended workflow. But the panel itself makes it feel cramped.
This is coming from someone with Server apps open, terminal windows, multiple instances of Finder, and so on. I'm sure for the average browser computer user it's adequate. But I just don't see a 13" laptop as really being a Pro machine unless you are truly willing to sacrifice portions of your workflow usage for smaller footprint.
For me, it's more about amount of screens rather than screen size. I can't REALLY do my job the way it's supposed to be done with less than 2 monitors, because I'm constantly in conference calls and presentations and often have to share my screen on one side while I do other things on the other.
On iPad Pro, my solution to this was that I would have all my work apps open in pairings and then I would just 4 finger swipe back and forth between different pairings. There were two major problems with this: 1) Most 3rd party iPad apps still don't fully support iPadOS multitasking, multi windowing, or slide over, so for work tasks, I was constantly having to re-open or re-situate my applications. I found workarounds for all of it, but still.......and 2) iPadOS does not allow me to share my screen out from the conference call software I have to use.
On the Mac if I have to work on just the laptop screen, I have Spaces. To me, that's the next best thing to having 2 monitors, and as long as I have that feature on the MBA, I can do pretty much anything. There is nothing finicky about it--it just works. It's one of the Mac's most underrated features, in my opinion. The stuff I had set up on a Space stays that way until I say otherwise, whether I'm constantly flipping back and forth or not. I don't have to worry about apps being compatible with the Spaces feature, because macOS treats it the same way as a second monitor. Whether that's on my 13" MBA or my 15" MBP doesn't make too much difference to me. I love the portability of the MBA.