Cloudflare appears to have zero impact on Google PageSpeed Scores for small business WordPress sites.

That's embarrassing.

My personal theory is that small business websites don't receive enough consistent traffic to benefit from the distributed CDN provided by Cloudflare. The CDN will only improve performance if visitors hit the cache repeatedly. Otherwise, a CDN can actually slow things down!

Good point. A CDN also won't buy you much without the proper Cache-Control headers [1]. I wonder how many of these sites installed the plugin but didn't bother to configure it properly [2].

[1] https://wordpress.org/support/article/optimization-caching/#... [2] https://support.cloudflare.com/hc/en-us/articles/227342487