If your tongue look like shit even after strict basic oral hygiene, you need a blood work for STDs, micronutrients deficiencies and see if you have a liver problem.
If everything is fine, then 5-6% of the population are genetically gifted with that type of tongue and it's harmless.
If not, like a geographic tongue, it can comes from psoriasis eczema diabetes or violent arthitris. So the diet need to be fixed first + using antihistamine pills, creams, mouthwash etc or aspirin.
Fissured tongue can be a byproduct of the crohn's disease so diet need to be fixed. Sometimes it can comes from autoimmune diseases so nearly impossible to be fixed
Chronic granulomatous disease can be the cause of bad tongue.