What Yoast actually does
Output control. Title and description templates, canonical tags, robots directives, XML sitemaps, breadcrumb and Article schema, and readability hints inside the editor. That is genuinely valuable plumbing, and it is where the category ends.
If you want a different plugin
Rank Math and SEOPress cover the same ground with more settings exposed for free; The SEO Framework is the minimalist option with the lightest footprint. Migration between them is largely automated, but always re-check canonical and sitemap output afterwards - that is where migrations break.
Why the green light is not a ranking
Plugin content scores check keyword presence, length and readability against fixed rules. They cannot see the SERP you are competing in, so a page can score perfectly while answering the wrong intent entirely. Treat the traffic light as a proofreading aid.
What a plugin structurally cannot do
Crawl your whole site and rank issues by traffic at risk, track positions over time by location and device, validate schema against current Google requirements, detect content decay, or tell you whether AI assistants cite you. Those live outside WordPress.
The sensible combination
Keep a lightweight plugin for tag output, and run analysis externally. SEO Smart Engine audits any WordPress site by URL - no plugin, no admin access - and returns prioritized fixes you then apply in whichever plugin you already use.