Let's go check out some websites and see how they're doing.

• Netlify
  On a first load on this page, we get popups on top of eachother. That's a horrible user experience. On the same page, part of the popup is transparent which ruins accessibility and makes it look quite strange.
  
  In 5 minutes I got 59 diagnostics.
• Battery Ventures
  They misspell "acquire" as "aquire" here, here, here, here, here, and here.
  
  They also misspelled the name of one of the firms that they invested in ("AppDynamics") in a blog post about them as "AppDyanmics" here.
  
  In 5 minutes I got 49 diagnostics.
• UC Berkeley
  They have pages that work really badly on mobile like this and this.
  
  They have dead links on this and this page.
  
  Oh, and they also misspelled "virtual" on this page
  
  In 5 minutes I got 103 diagnostics.

These aren't cherry picked examples. They are the norm.