On review of #Pixelfed open GitHub issues, it seems that Instagram import is very problematic. It's had issues handling things like dates newer than 2023, images without captions, .webp and .heic images, and video thumbnails.
https://github.com/pixelfed/pixelfed/issues?q=is:issue%20state:open%20import%20instagram
I'd hope Instagram import is a high priority for devs right now, at the height of Pixelfed adoption. It's pretty disappointing to find that it's not the easy migration from IG that we're led to expect.
I understand the challenges of software development and can be patient, but a lot of users will just give up.