Note also that many of the redesigned plugins will be slower than their older, mature counterparts. Give the plugin authors some time to optimize their plugins, and try to cull the amount of plugins you currently use. I've using only Adblock Plus, Tree Style Tab, and Tridactyl.
It's a Nokia 6.1. I've got a lot of apps running, so my guess is that memory exhaustion is causing the app to completely close when switching away. The whole app and previous page then needs to be reloaded when I reopen the app. I think it's the previous page reloading is causing the biggest part of the delay.
What's annoying is that even if I try to switch to another site, it still waits for the previous page to load. I'd like to easily cancel the reload so that I can go to a separate page quickly.
Even Edge is now chromium based, I think it's a lost battle.