Funnily enough reading studf from this site's (i.e. rank brain 2018 guide) on mobile makes my phone lag hard (octa core from last summer). I think the 5000+ heavy images content needs some mobile optimizing...
Here's a little audit with Chrome's own tools: https://i.snag.gy/eX7IB1.jpg
Jesus Christ didn't knew that. Someone told me few months ago that's the SEO guy & the way he talks & all is solid content. Didn't knew it has so bad LightHouse perf.
Really? Sites like that really set off alarm bells for me.