Quality and visibility are two different problems. Here is how to tell which one your book actually has.
A book can be well written, well edited, and warmly reviewed, and still sell almost nothing. That is not a contradiction. Quality determines whether a reader finishes and recommends your book. Visibility determines whether they ever open the first page.
Most struggling books are not quality problems. They are discovery problems: the wrong categories, keywords no reader searches, a description written like a synopsis instead of a hook, and no audience being reached deliberately.
Start by separating the two. Look at your listing traffic against your conversion. If very few people see the page, you have a discovery problem. If many people see it and few buy, you have a conversion problem. Each needs a different fix, and treating one as the other wastes months.
The practical order is: fix positioning, then metadata, then description, then outreach, then paid amplification. Spending on advertising before the listing converts simply pays to show an unconvincing page to more people.