Web accessibility is a vital component of user-friendly websites Nielsen's ten general principles for interaction design are informative. Indeed, for some like me, it is expedient to use UI frameworks in this process to save time and forgo the hassle of CSS3. However, I found the tradeoff to this approach; for instance, while surfing the web, I discovered some websites using UI frameworks are missing web accessibility like image alt to aid speech transcription for visually impaired users within the page source. I am not saying UI frameworks are the issue.
I only feel it can lead to negligence on web accessibility by leaving it to the UI frameworks. For instance, simple tooltips within text and image alts to help screen readers are left out. The developer (I am guilty) believes such issues were solved at the get-go by the UI framework. I believe it is helpful for developers to read the UI framework documentation but to go further and ensure that their projects meet the W3C standards.