I have had this problem for a long time on Windows 10. The CITI.com website is very very slow. Suspect scripts are performing slowly. Have tried this with shields on and off.
Running Chrome in parallel is 10x+ faster on basic tasks like menu picks, opening one of my account pages, etc.
I tried that and also cleared cache. Still sluggish compared to chrome. Here are some comparisons, from click to page fully loaded (X turns to refresh button):
Log into account shows account dashboard 13 sec vs 36 sec
Open credit card account 10 sec vs 26 sec
Open virtual credit cards 5 seconds vs 23 sec.
Generally while waiting the bottle left says waiting for citi.com or waiting for content. sometime just blank
Any other ideas. I like Brave and would like to help make it better.