I found that when logging into https://vault.bitwarden.com, several large JS files are loaded, which causes a blank screen in areas with poor network connectivity (like China). I suggest reducing the size of the JS files.
For me it is after entering https://vault.bitwarden.com/#/login and before the login screen shows up. I’ve tried different browsers (chrome, edge, firefox) and they all take ≥ 5 mins to load, and sometimes never. I believe the login screen loaded super fast a week or two ago and started getting slow just around the time this post appeared.
The login process after submitting the password is also somewhat slow (1~3 mins before the vault shows up) but probably reasonable for the large number of items I have. Edit: I tried another account with only 2 entries but it took the same time.
Once logged into the vault, the response time becomes normal again when I interact within the vault.