The first version of our web trading platform was written in Angular. It quickly got out of hand in complexity (and we felt Angular had a learning curve that was unwarranted for a frontend lib). The bundle sizes were also big. Then the Angular version fiasco happened. Vue turned out to be far easier to understand and work with, was faster in our benchmarks, and smaller in size.

With Flutter, we initially had a native Android app and a React Native iOS app. Managing two codebases was obviously painful, and React Native had significant performance issues, and we also struggled with the lack of stable libs, and the breaking changes between releases. Flutter came along and we were able to share 90% of the codebase across Android and iOS apps, and were quite happy with 60FPS rendering of native UI.