John Gill Commentary Deuteronomy 28:29

"and thou shalt grope at noonday, as the blind gropeth in darkness, and thou shalt not prosper in thy ways: and thou shalt be only oppressed and robbed alway, and there shall be none to save thee." — Deuteronomy 28:29 (ASV)

And you shall grope at noon day as the blind grope in
darkness
That is, being in darkness through the loss of their sight; otherwise the darkness and the light are alike to them, and they grope in the one as well as in the other.

This comparison shows that the darkness and blindness of the Jews, threatened them, is to be understood not of the darkness of their bodily eyes, but of their minds; not being able to understand, or form a judgment of things that are as clear as noon day; and being at the utmost loss what methods to take and pursue, when they are plain and manifest before them; but being infatuated and besotted, follow the lusts and counsels of their own hearts, which lead them wrong:

and you shall not prosper in your ways ;
in any steps they may take to extricate themselves out of their difficulties, distresses, and calamities, or to bring themselves into easy and comfortable circumstances; to get wealth and riches, and honour and esteem with men; but, on the contrary, become forlorn and miserable, poor and wretched, mean and despicable:

and you shall be only oppressed and spoiled evermore ;
continually, every day, all the days of their lives, oppressed with taxes and tributes, with mulcts and fines, and spoiled of their goods and substance under one pretence or another; which has been generally their case in Popish countries; for this seems not to refer to the Babylonish captivity, where they built houses, and dwelt in them, and planted gardens, and ate the fruit of them; and in the peace of cities had peace themselves, (Jeremiah 29:5–7) ;

and no man shall save [you] ;
from the oppressions, exactions, and spoils of their enemies, nor deliver them out of their hands; whereas in process of time they had deliverance and salvation from the Babylonish captivity, by the means of Cyrus king of Persia.