Hacker News Reader

I don't know if your system has a defect, but I've used many, many Macs over fifteen years on all released versions of macOS, and I've never once encountered the issues you're raising.

I think it's probably something between Mojave and Big Sur based on my recent upgrades. Sandbox is as good of an explanation as any.

It sounds like you may have a undiagnosed local networking issue. I’ve been using Macs since 1991 and the last time I had the sort of issue you’re talking about was classic macOS, where AppleTalk would literally hang the entire OS when it went into the weeds.

Network issues, diagnosed or not, should not affect the performance of local UI operations. "Don't perform I/O on the UI thread" has been a maxim for decades.