A lot of people have luck, especially for children, with The Specific Carbohydrate Diet, which eliminates all grains and starchy food, among other things. It's based on relatively outdated science, but it still seems to work for many people. (It was created when there was a very limited understanding of the microbiome.) There's an active Facebook Group full of people who follow the diet[0].

Seattle Children's Hospital [1] uses the diet as one of the primary treatment modalities.

Even if you don't choose to follow that diet, the primary goals should be to eliminate any inflammation, and also find foods that are safe to eat. Most people who do well, in terms of outcomes, learn to be very careful with what they eat. No matter what, it's a long term learning process. Eventually, you want to eat as diverse a diet as possible, while still avoiding any foods that are potential triggers for inflammation.

Unfortunately, most gastroenterologists are not knowledgeable about diet, and are not helpful, in terms of dietary treatments. I would recommend finding a doctor who is supportive of both dietary and drug-based treatments, as opposed to a doctor who has the blinders on, and sees drug treatments as the only option.

[0] https://www.facebook.com/groups/SCDers/

[1] https://www.seattlechildrens.org/conditions/crohns-disease/