How does a new KDP writer supposed to market a book?

Because you cannot persuade readers to buy any book in which sentences do not make sense. This shouldn't be “does.” If you don't see the problem, that is a big problem.

Are you planning to proofread your book to avoid sentences such as

B) that are filled to the brim with typos or errors.

POLL: ESPN writer stokes the flames of Lions trading for All-Pro EDGE - Pride Of Detroit

C) that are unreadably terrible in any other way.

If your book is well presented, well written, and basically free of typos, then

How does a new KDP writer supposed to market a book?

This overlooked cause of PTSD is only going to get worse - vox.com

E) Take a solid year to learn how to use Amazon or Facebook ads and be prepared to lose quite a bit of money as you figure it out.

C) Persuade book reviewers on BookTok or Substack or someplace to recommend your book. If your book is unreadably terrible, this is probably impossible.

A) that are not actually books.

Aldi accused by Oreo maker Mondelez of copying its packaging - CBS News

Or

D) that are presented with bad covers, bad descriptions, or ludicrously bad interior formatting.

You cannot effectively promote books

WCWS Game 2: Texas Tech evens series with 4-3 win, setting up decisive Game 3 - Yahoo Sports

A) Build a following on social media, a following of people who will buy your books. Good luck with that. There is very little evidence that social media can translate to sales.

Or

B) Build a newsletter mailing list of people who will buy your book because they trust you to write books they want to read. This is slow, but ideal.

Is there any evidence to support the existence of people who have experienced "gangstalking"? Or is it a psychological phenomenon?

D) Pay promotion services like Written Word Media to promote your book. Legitimate services will not accept your book for promotion if the presentation is crappy or the book is badly written.