Sure, and the moon landing used computers with less processing power than your kids calculator. That doesn't mean we should use those to put people on the moon over faster hardware.
Does the fact that older, slower and smaller hardware and software once existed mean we should spend time, resources and potentially sacrifice features to... what? Hark back to the old days where we had 128kb of memory and hard disks the size of vinyl records?
A 6mb GUI app _is_ impressive for right now. At some point in time it would have been absolutely massive, and the way it's going, at some point in the future it may well be absolutely minuscule. And that's not a bad thing.
In general, complexity is indicative of a poorer design, and the fact that an entire operating system + utilities can be delivered in a comparable size to a gui app is hard to look away from.
The author says, "Once you accept bloat, it’s very hard to claw it back". The fear is that bloat increases at higher rate in proportion to its capability and computing power.
I'm cognizant that I'm very much in the minimalist camp with regard to computers, so I do make sure to peek outside and remind myself that stressing about an executable size is a bit unwarranted. But that being said, we must remain vigilant!
If you want to use windows as an example. Why not take the current version? It uses what like 16GB for a basic install (I wouldn't know, I don't use it)? Compare the 6Mb GUI framework to that.
Windows 3.11 required 4MB of RAM and the whole install took <20MB of disk space, and that's the entire OS with all of its utilities and libraries.
A typical smartphone ships with around 10,000 times this much storage capacity and enough RAM to hold it 100 times over.
The fact that it can hold that much does not make it right to waste resources. To contrast, video or audio is a good use of the space it takes up in general, because there has been and continues to be research in compressing that data, and it's pretty close to being as small as it can practically be. Apps are not a good use of space because we know roughly what the lower limit is --- and the current average is a few orders of magnitude more than that.