Through my entire career, I’ve run into people that didn’t believe that WordPress could scale. They looked at sites weighed down by poorly coded themes and plugins or just made assumptions based on experiences from a long time ago.
WordPress can scale to meet the needs of any size website if developed and managed correctly.
One of the clients I worked with a few years ago was a non-profit organization that was building an audio management system on top of WordPress using the new-at-the-time WordPress REST API. Their project garnered more and more attention until Google decided they were going to promote it.
I was working with a team that was responsible for the server platform that this nonprofit was using and the news about Google came in only days before the promotion was to happen. The project was going to be linked to on the homepage of Google, right below their iconic search input box.