Ask HN: Why has the Google Play Music web app become so poorly performant?

I use Google Play Music for work and their last two UI "upgrades" have had dramatically and detrimentally negative effects to browser performance.

I know this is going to sound like a complaint or a support request, but I genuinly want to know the cause of the poor browser performance. I'm sure GPM is a fairly complex SPA, but it seems that the javascript has gotten out of hand. Looking at the Network tab of the dev tools shows a lot of requests (151), and 2.5 minutes just to refresh!

aren't there service workeres to help with t his sort of DOM blocking maddness?

It seriously took 6 minutes of blocked DOM just to get the feedback form up.

I have tried several systems, different browsers and incognito and it seems to have no effect. Firefox even gave me 4 alerts that there was a unresponsive script, and even offered to kill it.