Fiber is indigestible and not required for human health. It's also a cause of bloating, constipation and gas... because it's indigestible. Fiber does have the benefit of slowing sugar digestion, but you can and should just eat less sugar. Some forms of fiber can be converted to fatty acids by bacteria in your colon, while also producing other byproducts. You can get those fatty acids by eating more meat without the added stress on your digestive system.

Compare the human digestive system of a human being to a wolf (carnivore), a pig (omnivore) and a gorilla (herbivorous hindgut fermenter). The human gut by proportions sits somewhere between wolf and pig.

Look up the actual studies on fiber rather than pop science articles, and examine them critically. They'll do things like assume that pooping more often and having a greater volume of poop is healthier, with no basis. Things like how easy it is to poop or feelings of being bloated are harder to quantify, so they're typically ignored.

Or you get the extrapolating cancer risk based on some vaguely understood biomarker, which is one step below "in mice" as far as science goes.