Why Is Google Takeout So Slow?
Google builds your export from scratch and throttles it. Here is what actually speeds it up.
Because Google is not handing you a folder that already exists. It is walking your entire library, pulling every file out of storage, and packing it into zips. For a large library that is genuinely a lot of work, and it is queued behind everyone else asking for the same thing.
A few days is normal. A week is not unusual for hundreds of gigabytes. Requesting it again does not jump the queue; it starts over.
What does help: ask for Photos only rather than all fifty Google products, and choose a smaller archive size so parts arrive and can be downloaded as they finish.
When it does arrive, the slow part is over and the annoying part begins: every photo carries the download date instead of the date it was taken. That fix takes one run rather than another week of waiting. The first 500 photos are free.