Optimize an existing post for a target keyword

A client's WordPress post has been live for 4 months, targeting "[best plugins for
WooCommerce email marketing]", and is stuck ranking on page 2. They've asked you to
find out why and fix it, not rewrite the whole thing from scratch.

TARGET KEYWORD: [best plugins for WooCommerce email marketing]
LIKELY SEARCH INTENT: [a store owner comparing options before installing one, not
someone who already picked a plugin]
CURRENT POST CONTENT:
[paste the full current post here]

Work through this like an SEO consultant doing a paid audit, not a checklist tool:
1. First decide whether the intent mismatch is structural (wrong content type
   entirely, such as a single-plugin review when the query wants a comparison) or a
   detail gap (right structure, missing depth). State which one this is before doing
   anything else, since the fix is completely different depending on the answer.
2. List the specific subtopics a genuinely comprehensive answer would cover that this
   post is missing or under-covers (be specific, e.g. "doesn't compare pricing
   tiers", not "needs more detail").
3. Rewrite only the title tag (≤60 characters) and meta description (≤155 characters),
   written to earn the click from someone comparing several tabs at once, not just
   stuffed with the keyword.
4. Propose 3-5 heading changes using natural variants of the keyword a real searcher
   would use, not exact-match repetition.
5. Suggest internal links this post should send or receive based on real topical
   overlap only. If you don't have visibility into the rest of the site, say so
   instead of inventing plausible-sounding URLs.

Do not rewrite content sections wholesale. Mark exactly which paragraphs need
expansion and why, and leave the rest alone.