If you define “good gut health” as “having the bacteria that process fiber”, then OF COURSE eating fiber is good.
But...is fiber actually good for anything?
As someone who has eaten a very low fiber diet - almost fiber-free - for years, I don’t know what the benefits would include.
Acetate, butyrate, and propionate are all very helpful to cellular processes. Soluble fiber specifically helps bacteria that make these for us.