Replace PageSpeed Insights only if you are clear about which half you mean: the field vitals, or the lab advice.
Field-data alternatives
Search Console's Core Web Vitals report and a real-user monitoring tool are the alternatives when you need more than one URL. PageSpeed Insights is a window onto the same Chrome field data. Switching products does not create traffic you do not have.
Lab alternatives
Lighthouse in Chrome and WebPageTest are the alternatives for a controlled run. Use them while you change the template. Re-test the same URL. Do not average five pages and call it a program.
The SEO alternative
Fix SEO Today does not replace the vitals report. It answers the questions speed tools skip: is the page indexed, linked, unique, and citable. Run that when the speed score is a distraction.
Lab is a simulated browser. Field is your users' devices and networks. Fix the template with the lab. Judge the result with the field.
Will a better LCP fix rankings by itself?
Sometimes it helps a page that was already relevant. It will not index a page your robots.txt disallows.
Why is Fix SEO Today cheaper?
PageSpeed Insights is free. The suites sold as a fuller speed platform are extremely expensive. Fix SEO Today is cheaper because you pay for the diagnosis. A free peek, then $19 a month for one project or $99 a month for unlimited projects. That covers the crawl and the plain-English fix list, including GEO. It leaves out the backlink index, the rank-tracker seats, and the ads module.