The checkup is deliberately blunt about what matters. A missing page title is worth fixing before lunch. A slightly imperfect heading order is not worth your afternoon. Work from the top and stop when the remaining items feel cosmetic, because they probably are.
The accessibility check is the one people skip and should not. Missing photo descriptions and text too faint to read affect real customers, and about a quarter of New Zealanders have some difficulty reading a screen. It also overlaps heavily with what Google rewards, so fixing it pays twice.
The speed check is almost always about photos. One enormous image is the usual culprit and replacing it usually moves the whole score at once.
Step by step
Open the SEO tab and pick a page from the dropdown.
Read "Your page" first. A missing title or description is the highest-value fix on the list.
Then "Can everyone use it".
Then "How fast it loads".
Fix, publish, and run it again.
If it does not go to plan
It says my links are broken and I do not think they are.
Tell us. We only report a link as broken when the server gives a definite error, so a false alarm is a bug on our side rather than yours.
It scores badly but the page looks fine.
Looking fine and being findable are different things. A beautiful page with no title is invisible in a search result.