Fix Google Search Console indexing issues on large WordPress site (60K+ posts, ~420K pages affected)

BACKGROUND:
We run a large WordPress celebrity biography/entertainment site with 60,000+ published posts. Google Search Console's Page Indexing report shows multiple issues affecting how pages are crawled and indexed (full breakdown below). We need someone to go through these systematically: diagnose the root cause for each issue, fix what should be fixed, and confirm what is intentional and fine to leave as-is.

Tech stack: WordPress, PHP-FPM 8.3, MariaDB, Nginx, aaPanel, Cloudflare CDN, Envo Magazine theme (child theme active), custom mu-plugins for SEO, schema, and interlinking.

CURRENT SEARCH CONSOLE BREAKDOWN:

Crawled, currently not indexed (Google systems) - 419,967 pages
Excluded by noindex tag (Website) - 96,257 pages
Alternate page with proper canonical tag (Website) - 38,431 pages
Not found 404 (Website) - 31,943 pages
Page with redirect (Website) - 15,718 pages
Discovered, currently not indexed (Google systems) - 64,738 pages
Duplicate, Google chose different canonical than user (Google systems) - 1,010 pages
Duplicate without user-selected canonical (Website) - 2,454 pages
Blocked by robots.txt (Website) - 804 pages
Server error 5xx (Website) - 98 pages
Soft 404 (Website) - 20 pages
Blocked due to other 4xx issue (Website) - 2 pages
Redirect error (Website) - 1 page
Blocked due to access forbidden 403 (Website) - 1 page

SCOPE OF WORK:

1. Audit each issue category above. Pull URL samples for each one from Search Console, identify the actual cause (template issue, plugin behavior, server config, intentional noindex, genuine broken link, etc), and report back before making changes.

2. Crawled and Discovered, currently not indexed (the two biggest categories, around 485,000 pages combined). Investigate what is driving this at scale. One known contributing factor is thin or near-duplicate tag archive pages (we use a custom tag slug "/profile/" for celebrity name tags, some of which have a full dedicated post, some of which are only mentioned within other posts). There may be other URL patterns contributing too, such as paginated archives with tracking query parameters. This needs full investigation, not assumptions.

3. Not found 404 pages (31,943 pages). Identify whether these are old deleted posts, broken internal links, malformed URLs, or external sites linking incorrectly. Fix internal links where we control them, and redirect or otherwise resolve where appropriate.

4. Duplicate content issues (2,454 plus 1,010 pages). Identify URL patterns causing this and implement correct canonical tags.

5. Noindexed pages and canonicalized pages (96,257 plus 38,431 pages). Confirm these are intentional, such as paginated, tag, or archive pages. Flag anything that looks like real content being excluded by mistake.

6. Server errors, soft 404s, robots.txt blocks, and redirect errors (smaller counts but still real issues). Investigate and fix each one individually.

7. Implement all fixes safely. Theme changes must go in the child theme only, never the parent theme. Any template changes must not break other page types. Test before full rollout on a 60,000+ post production site.

DELIVERABLES:

Written diagnosis for each issue category with example URLs and root cause
Implemented fixes such as code changes, redirects, canonical tags, and robots.txt rules
A before and after tracking plan to confirm Search Console numbers improve over the following weeks
Documentation of every change made and how to roll back if needed