Please help me determine which system uses the site usefulls.info
I don’t think it is wordpress but what…
More like HTML/PHP website but sure not CMS
WordPress is most effective and the best CMS. Why will you think about others CMS?
WordPress is good, but not the only
In case you want to make projects that are not related to commerce (such as the presentation of a corporation) I strongly believe that WP is one of the best (if not the King) options. Strong community, a ton of plugins, well documented etc.
It supports also commerce handling but I personally find it strange for a product to behave like a post page (with commerce features – wp/woocomerce).
For commerce projects I suggest solutions that were born for commerce.
As for custom vs open source project my opinion is: Definitely open source. In short terms: Many developers patching the same issue. Many people working with the same ecosystem, that is to say many plugins. Updates every now and then. Free stuff. Getting to know other community members (of the same forum community) etc.