It used to be much harder to track certain aspects of SEO ROI. But, with advances in online tracking, that gap has been bridged for the most part. Some aspects of SEO are still somewhat difficult to give direct attribution to and therefore calculate ROI. However, nowadays you can track everything from how users engage with your website to how effectively a page converts users into leads to the impact of offsite SEO.
While we don’t know exactly what Google’s algorithm is looking for when it crawls a site, we do know that Google looks at a website as best as it can through the eyes of a user. If your site has the necessary elements a user is looking for and it’s easy to use, then your SEO is likely on point.