Loads quickly for me. I keep hearing that LinkedIn loads slowly but people fail to mention specifics about their devices and internet speeds. Are you on home wifi, LTE or something else?
Jira is especially cumbersome as when you update one thing it refreshes half a dozen other items and you have to wait for the whole lot before it becomes interactable again. In those cases, I would prefer it either to update on the component I touched or to not pretend to be reactive and just be a flat out form POST.
As it stands it is the worst of both worlds and the network delay compounds to make it a slow, page jittering mess the whole time I am using it.
Even on a desktop I get a loading screen for maybe 2 seconds and the site loads in ~4 seconds.
A modern website that works well on all devices quickly is soundcloud. Seamless browsing/listening and excellent user experience.
It seems like devs tend to ignore network latency entirely because it's something outside of our control. It seems to be getting worse too, things like the windows start menu can freeze when you're on a intermittent connection, SPA's can break entirely. I've spent a good chunk of my career fixing n+1 problems over a network, even when it's on a fast connection to a local database the latency becomes noticeable are fairly small values of n.
Polymer in particular is notoriously slow when using polyfill.