Yesterday (November 3rd, 2021), Google released a 2-minute, 11-second video titled SEO Lightning Round 2. I presume the word lightning refers to the video’s rapid succession (and answering) of the 4 questions that were addressed.
The video featured Google Search Advocate John Mueller, who read and quickly addressed these questions--all of which had short, straight-to-the-point answers.
The first question was about mobile-friendliness, and asked:
“When we block CSS files on the CDN through robots.txt, the report on mobile-friendliness in Google Search Console is red. Would this affect the actual ranking?”
John’s response was:
“The short answer is, yes, it can cause issues, and you should avoid doing that. Being able to see a page completely helps us to better understand the page and confirm that it's mobile-friendly.”