To properly analyze a site , Run an SEO audit , Test website speed , Perform competitor analysis.
SEO analysis and auditing tools ( SEMrush , SpyFu , Moz )
Website speed and performance tools ( Sematext , Pingdom Speed Test )
Competitive analysis tools ( Google AdWords Keyword Planner , SEMrush , SpyFu )
Ahref (It is mainly used to analyze a website's link profile, keyword rankings, and SEO health. And it use to conduct keyword research for Google, YouTube, and Amazon. And many people use Ahrefs to find content that's performed well )
Above these are some of the best tools for analyze a site .