Adam Clarke on Exodus 6:9

But they hearkened not - Their bondage was become so extremely oppressive that they had lost all hope of ever being redeemed from it. After this verse the Samaritan adds, Let us alone, that we may serve the Egyptians: for it is better for us to serve the Egyptians than that we should die in the wilderness. This appears to be borrowed from Exo 14:12.

Anguish of spirit - קצר רוח kotzer ruach, shortness of spirit or breath. The words signify that their labor was so continual, and their bondage so cruel and oppressive, that they had scarcely time to breathe.