I saw a discussion on HN earlier today criticizing SPAs for offloading data processing to the user's machine, benefiting Facebook/Google/big tech at the expense of the user experience. I think that conversation sometimes misses the positive side of React/client-based apps.
MockRocket and other web-based creative tools demonstrate the strength of the web as an application platform, making complex tools more accessible and easily distributed than before. Derek's built a pretty slick editing & rendering experience that allows more people access to video editing, without having a powerful machine with a GPU. I'm incredibly impressed with the rendering fidelity he's been able to build into MockRocket and excited to play around with it more.
Another great application is https://www.photopea.com/ -- a pretty powerful photoshop competitor that also works exclusively in the browser. Looking forward to seeing more people build and distribute creative/technical tools that more people have access to.