POP3 is good for use cases where you're rapidly migrating out and you want to wipe the messages clean, server-side. Or, if you believe the server will play hijinks with your messages or folders in some way, POP3 will give you a snapshot from time of download.
I always have a failure with Google Fit data, which reports 'Service failed to retrieve this item' on the same JSON file every time. I assume this is something corrupted at their end.
It's not that uncommon for my exports to intermittently show failures with other services -- for example, my latest export, taken on April 20th, also failed to include one of my YouTube videos, with the same 'Service failed to retrieve this item' error. That video is usually included successfully, so I'm guessing this was a glitch.
Nothing major, but I can well believe that others also experience regular errors, although I'm sure we're in the minority.
You just click the boxes for the services you want, it e-mails you when it's ready minutes/hours later, and you download the file(s) at the speed of your internet connection.
Considering it has to zip up many gigabytes of data from various sources, it works at an entirely reasonable speed.
The idea that it's too slow to be of value is a reason not to use it makes no sense.
Do you just not make backups of your data at all, because backups take hours?