With WordPress, it's important to differentiate between support for the application itself, and support for third-party components that integrate with WordPress like "plugins" (functionality) and "themes" (web design templates).
The WordPress application provides free support via an online community of general users and technical experts (e.g. developers). This support is mostly related to reporting bug fixes, security vulnerabilities, etc., which then get reviewed by the core development team for possible implementation and resolution in the next or a future version upgrade.
Most of the problems users experience with WordPress, however, tend to come from third-party plugins and themes causing conflicts or errors. These are developed by a range of different providers, developers, designers, amateur coders, etc. and so the level of support varies. Just like "apps" for mobile devices, there are developers who create robust solutions that play well with everything else on your device and they provide excellent support to users, and there are "fly by the seat of their pants" developers and/or marketers who rush out software that is really "buggy", or they don't have a great customer support structure in place to handle issues and provide solutions quickly (or at all).
I gave the rating of 8/10 in this case, because if you focus on the support you can expect to receive for "core" WordPress-related issues only (e.g. bugs or vulnerabilities in the software), there is no dedicated WordPress support "representative" that will directly assist you or manage your case - it's an open source community. And if you focus on the support you can expect to receive for third-party plugins and themes, then that varies greatly depending on who the plugin or theme developer is, and whether you are using a free or premium plugin or theme.