1 Cor 1:23
This portion of text doesn’t addresses Isaiah’s curse.
If the Greeks aren't under the "curse" in Isaiah then how come Christ Crucified is foolishness to them?
Does a person have to be under a curse to find a message to be foolish? I am not convinced that being under a curse is a prerequisite for finding things to be foolish. Nonetheless, the answer to your question is in 1 Cor 1:18, “For the message of the cross is foolishness to those who are perishing”.
Romans 1:20-25
This portion of text doesn’t address Isaiah’s curse. Instead it deals with God revealing Himself through nature and the implications for humans in general, even though I’m under the impression Paul had Jews in mind and not so much humans in general; but that’s another topic for another time.
Again, we know that the Jews were under a curse via the writings of Isaiah, John, Paul, and Jesus. We also know via the Scriptures that the curse was pronounced on the Jews, and no such pronouncement was made upon Gentiles. In addition, we learn from the Scriptures that there was a significant difference between the way the cursed Jews responded to the Gospel and the way the non-cursed Gentiles responded to the Gospel. So, again, the Scriptures make a distinction between Jew and Gentile in how they'll respond to the Gospel, and this distinction is based upon Isaiah's curse. Neither of the passages you cited address Isaiah's curse and its impact on the Jews.