The entire web app is JS based. It's a requirement I'm ok with.
And to answer your question, you're seeing that kind of styling so frequently because it's likely part of Framer Motion, an extremely popular animation library
Is the website machine generated? Besides the hard-dependency on JavaScript, this also causes the exact same problem I've seen on another[1] machine generated site: https://postimg.cc/TyMBfVZ6, https://postimg.cc/n9j1X5Dk. This happens randomly on refresh on Firefox 148.0-1.
Is the fade effect really worth having parts of your site disappear at random?
And to answer your question, you're seeing that kind of styling so frequently because it's likely part of Framer Motion, an extremely popular animation library
https://www.npmjs.com/package/framer-motion https://www.npmjs.com/package/motion