If it were just the risk of brute-forcing, I have a hard time believing this to be a real problem. Use a secure enough passphrase etc (and if that's not good enough, they could also just brute force into most of your accounts anyway). IMO the relevant thread model is more that they can convince / coerce / do it themselves the provider to change the javascript that does the client side decryption.
I use bitwarden for a good fraction of my login data, because I don't currently consider this part of my thread model...
I'm not fully convinced by bitwarden, especially the 2nd factor integration IMO isn't good enough. But I've not had enough to time to look much further.
I wish there were something that used (as a second round of encryption) a key residing on a yubikey to decrypt the password of individual entries, without going through gpg. Going through gpg just seems to complicated and fragile to me, and has annoying restrictions like not really allowing multiple yubikeys.