To Address a Few of the Misconceptions about WordPress
React is not used throughout the WordPress world. Wordpress.com uses React for its backend admin (Calypso) but the self-hosted version of WordPress provided by wordpress.org does not use React in its admin area except where a plugin developer specifically adds React to his/her own plugin or theme.
Gutenberg is a re-imagining of the WordPress content editor. This is written in React. Gutenberg is not a core component of WordPress and will not be until at least WP 5.x is released. As we know, Gutenberg will soon be rewritten to use something other than React.
Many of us in the WordPress community are happy Gutenberg has been delayed. Although it is evolving into a nice product to use, Gutenberg is a big shift from a straightforward TinyMCE editor whereby an author creates content as he/she would with a word processor toward a blocky lego brick wall style editor whereby an author needs to add different content blocks to add different types of content. Additionally, Gutenberg lacks many features of the current editor framework that plugin and theme developers rely on, though this is being addressed by the Gutenberg team. Both Vue and Preact are in the running to replace React. I think Vue will win the competition.
The WordPress REST API allows developers to build apps on top of WordPress. It can be used in both the frontend and the backend to interact with WordPress. WordPress.org does not use the REST API by default i.e/e.g. the display of posts in the frontend of the website is not generally created via interaction with the REST API.
Regards WordPress is not a framework like 'Laravel, CakePHP etc...'. That's correct. It is not supposed to be. WordPress is a content management system that facilitates database management, interaction with a database and presentation of data stored within a database. There are hooks and filters built into WordPress that allow developers to interact with WordPress code execution. Additionally there is the REST API.
There are lots of content management systems available, few of which are as adaptable, as well supported and as well liked as WordPress but then there are some that are better suited to specific tasks for which WordPress is overkill. For example, if you want a blog and only a blog then choose a flat file CMS that is built for bloggers.
I've used and supported WordPress, Joomla, Drupal, Magento, Simple Machines Forum, CMS Made Simple, custom built CMSs, Business Catalyst and many other CMSs and I can say with experience that WordPress is popular and widespread for good reasons: namely, it works, it is extensible, it is inexpensive and it is easy for authors and site admins to learn to use.
For those like to talk badly about WordPress because they think they know something they do not, if you're going to slag something off you should at least get up-to-date first hand experience of what you are gossiping about.