[2021] how long does it take to generate a world?

On hardware that meets the Minimum hardware requirements, making an 8k map takes on average 50-60 minutes.
On hardware that meets the Recommended hardware requirements, making an 8k map takes on average 15-25 minutes.

13 minutes to generate a 4K map for me - I’ve been making a lot of them recently. So your results sound typical. Also be aware that this is a... let’s say known inconvenience and a major area of optimization for the next alpha.