I doubt it that EAT can cause a penalty; then lots of other websites would be hit too. i think it comes down to authority of the domain. EAT can help in some niches for sure. There are sites that have good content, no EAT and they keep climbing the serps. why? one of the main reasons is time on site and CTR for the sites - as the content is engaging, good, it provides value to the visitor; thus depending case by case, niche per niche, there are different factors for each niche and some have more importance overall than others.