My first ever stab at french fries, and 20 minutes with olive oil and seasonings in the oven preheated at 450*F was not enough to make them crisp. They were cut thick.  Could I simply cook them longer to dry them up? They have the texture and consistency of a baked potato.... except the skins are crisp 
There are a few questions on this site about French fries, I'd suggest you take a look. But I think the best answer is: baked sticks of potato do not French fries make. French fries are deep fried. You can never get the same results in air, although air fryers do come close. A normal oven bakes, not fries.  Here are some sites that experiment with fries and crispiness [1] [2]. 