If you're mostly familiar with the WordPress CMS regarding optimization techniques, it may be difficult trying to learn how to optimize another type of website such as BigCommerce platforms or a custom Github website, for example.
For these websites, you may have to find other ways to optimize for SEO that aren't as convenient as the WordPress format. One of the ways to figure out how to optimize for SEO on another website might include looking at guides that detail the CMS, if it's difficult to figure out. Another way may be to simply work around certain inconveniences such as a website that doesn't include simple formatting for subheadings and other aspects of SEO. In this case, having a good understanding of basic HTML can provide you with enough of a workaround.
If you're unsure about how to optimize your given platform, the best solution could be to contact the support team behind it for assistance, or work with an SEO company who may be able to assist you. However, if you're familiar with WordPress and have the opportunity to stick with it, it's advisable to continue using it if other platforms are viable options for a business, blog, or other type of website. WordPress.org and advanced plans for WordPress.com both have solid SEO functions that can significantly help your website.