Absolutely - variant limitations have caused many store owner’s difficulty.
The image issue is also another one - with the failures, it will tell you why it failed in the export error details. Many times a whole product will error out if one of the images errors out! it’s definitely a pain, but takes some elbow grease to keep modifying the spreadsheets and pushing those uploads through.
Eventually It gets fun when you offer it as a service (or maybe that’s just wishful thinking on my end).
But I’ve done the same and used my own server to host and transfer images. It’s a pain to get going, and for many people the amount of ‘technical hurdles’ involved will also put them in a bit of a tough scenario.
Easier to let someone else do it. But could be costly as well depending on the amount of work.
100K images by hand though? holy *. Haha.