If I wanted to make money off a writing hobby I'd switch to textbooks. I list everything as public domain because I'd prefer to keep amateur status, without any of the obligations that come from taking money for a story.
I never heard of this Inkitt site so I can't comment on it. If I buy a book for entertainment I want a known quantity, an author with a good reputation, or someone who has a track record with short stories in a magazine. I don't see paid story sites building the equivalent of Youtube career influencers. If someone thinks they can charge for the story, go for it but I'd suggest handing out the first story for free, to establish some credibility.
The highlighted warning would give me pause before submitting any stories. This is similar to the ambiguous and arbitrarily enforced policies at Literotica. No argument the website owners can pick and choose as they please, but to me it isn't worth the hassle. I'll stick to this little corner of the Internet.
Jack Peacock