In case you do not know what is Google PageSpeed insights? Pagespeed insights from Google is a grading system, to determine the speed of the website loads using their grade based on Google Lighthouse.
However, many have the perception it is a very important grading system because Google owns the largest search engine on the internet. A slow website will affect your ranking.
A grade is a matrix determined by someone to compare or judge the differences on somethings. Speed is a perceived performance of how a person feels. So, what I’m saying the search engine bots do not grade but if your site loads faster, you are reachable, more pages are indexed. There are a few factors to rank your website higher, speed is just an element but not the entire of SEO.
There are many online tools grade your website speed and help you to debug JS and CSS on your website. You should not be limited to PageSpeed insights only. I have seen websites have a very low grade in PageSpeed insights but high in Pingdom and GTmetrix and the other war round.
So, I suggest if you are making a website, you should test your website’s speed with a few tools, not limited to Pagespeed insights. Also, do some comparison with your competitors’ website. If you are using WordPress, by nature a WordPress might be slower especially if you have many active plugins. f that’s the case, a cache plugins might help to reduce your website load time.