Louis van Gaal's men maintained their three-point lead over Belgium, who edged out Wales 2-1, at the top of Group A4.
They will need only a point from their last game against the Belgians in Amsterdam on Sunday to be sure of securing top spot.
The Dutch appear to be in strong form ahead of their World Cup opener in Qatar against African champions Senegal on November 21, before further Group A games with the hosts and Ecuador.
Poland qualified for the World Cup with a play-off victory over Sweden but were toothless on Thursday.
The Dutch took a 14th-minute lead after an excellent team move ended with Denzel Dumfries squaring for Gakpo to tap into an empty net.
The PSV Eindhoven winger has now scored eight goals in his last seven matches for club and country.
Poland finally created a good chance in the 53rd minute, but Arkadiusz Milik blazed over.
The Netherlands doubled their advantage seven minutes later as Vincent Janssen teed up Steven Bergwijn to score.
The winger has enjoyed a fine campaign so far, with eight goals for Ajax already since his Dutch-record move from Tottenham Hotspur in July.