The bottom line on floppy disks, in my view, is that they're a design compromise out of late 1960s technology.
The platform (drive) is made to be inexpensive (for the time), as is the media--all limited by, at best, early 1970s technology. Back then, almost all drive spindles were belt-driven and the small-format 5.25" drives used DC motors with rather imprecise speed control. Issues such as ISV (instantaneous speed variation) were rife, so the encoding and decoding of information had to be very tolerant of speed anomalies. In addition, the media had to be interchanged between drives, which brings up the hobgoblin of accurate track positioning. Drives are essentially "dumb" devices, so there's no provision for any sort of closed-loop system. When I first ran across the things, I was amazed that it worked. You had a medium that could be interchanged between "dumb" drives, and it was accessed with heads that contacted the surface of the disk. Could we do better? Absolutely, but the cost of the drive goes up. Consider an early 1980s attempt by Drivetech (later sold to Kodak in a bankruptcy sale). 192 track per inch with embedded servo, yielding, at first, about 3MB per floppy, eventually going to 6MB. The humble Zip disk (and the UHD disks) could get well more than 100 MB on a floppy, using more state-of-the-art technologies. Coatings have improved considerably over time, but the humble floppy is still powdered rust stuck to a plastic disc. Curiously, the notion of a flexible disc dates well back to the 1950s, when it was promoted for audio recordings that could be tucked into an envelope and mailed. The Zip disk was as close as we got to a universally-accepted candidate for replacing the humble floppy drive. However, it came too late. The same story applies with alternate encoding technology. For general acceptance, MFM was pretty much the end of the line. Earlier attempts used group-code encoding. Others used "zoned" recording to pack more data on the outer cylinders than the inner ones. But these all required the hardware peculiar to the system that created the disks. For all intents and purposes, the MFM 500KHz data rate encoding was the end of the line. Extended density media and drives used a 1MHz data rate to get 2880Kb on a disk failed miserably. The barium-ferrite media was never cheap and the drives were not widespread. I think it's remarkable when you think about it, that early 1970s 8" floppies are still quite readable today. I wonder if USB flash drives will endure similarly. We already know that stuff stored on the Internet won't. --Chuck