Hi,

I did not complete the quest but 1.21. ended it... now it's a failure. - Any suggestions?

Read the Patch Notes.

"Quest titled Collect 'Em All is now marked as failed if player does not succeed in collecting Milva, Vampire Bruxa and Dandelion gwent cards during gwent tournament in quest titled A Matter of Life and Death."

I think it's a good change, that every of the missable cards now results in a failed quest. It should have been like this from the start.

This is normal. You did not get some cards (missable ones) therefore the quest failed.

Well if that's your jam feel free to also have fun with them literally.