I see it all the time, applications that would be very usable and streamlined for users from a ui perspective are frustrating and painful to use because every action requires a multi second request. So the experience is mostly reduced to staring at progress spinners.
This is doing a lot of heavy lifting. Just because an app is slow doesn't mean Rust would've made it faster. It may just be slow because of a bad query or otherwise poor architecture, especially in web development. The commenter is asking what projects you've seen fail because the language itself hit a performance limit that couldn't be worked around.
this honestly sounds like you're describing the most successful software on the market. I can't think of many social media sites slower than facebook or instagram, or chat slower than slack or email clients slower than gmail.
