It's not necessarily that your tummy loves unhealthy foods (good news!), but stuff like cookies are what people refer to as slider foods (not so good news haha).
Slider foods are are soft simple processed carbohydrates of little or no nutritional value that slide right through the surgical stomach pouch without providing nutrition or satiation. When slider foods are consumed, they go into the stomach pouch and exit directly into the jejunum where the simple carbohydrate slurry is quickly absorbed and stored by the body. There is little thermic effect in the digestion of simple carbohydrates like there is in the digestion of protein so little metabolic energy is expended.
The most commonly consumed slider foods include pretzels, crackers (saltines, graham, Ritz, etc.) filled cracker snacks such as Ritz Bits, popcorn, cheese snacks (Cheetos) or cheese crackers, tortilla chips with salsa, potato chips, sugar-free cookies, cakes, and candy.
Definitely keep talking with your doc and nutritionist if you continue having issues with solid foods. Maybe try some vegetarian options that are higher in protein, like chili with beans but no meat. Good luck and keep us posted!