I think that depends on the “Grader” you are using. I think some give you excellent information, I find the “Grade” they assign usually to be ambiguous.
Without knowing what you are talking about, it’s impossible to say if you can fix it or should.
I don’t know that one, as a general rule, I don’t do anything with any ”SEO” companies or anybody that wants an email address before they’ll give you any results.
Since I won’t give up an email address, I can’t see what JavaScript library they might be talking about.
it says at the bottom it’s powered by Google lighthouse.
You can run that with a chrome extension as well. Google’s PageSpeed insight (also uses lighthouse) might be a better way to review some issues.
Unless you’ve put JavaScript in yourself there’s probably not much you can do about any complaints that test tells you about.
Somethings like using cache, optimized images, etc, etc you can address.