Does every browser just “encode” password lists like that?

It's the decryption key for the encrypted passwords which is encoded (I know confusing). But, they may as well not be encrypted for all the good it's doing you.

Off the top of my head, Chrome does this. MS Edge, which is Chrome with a blue coat of paint, does. Opera is Chrome with red paint, so it's almost certainly base64 as well. Brave browser is Chrome with orange paint.... You get the idea, lots and lots of "independent" browsers are just Chrome (ok technically, Chromium, the open source version of Chrome) which mean they inherit all it's faults. I don't know the scheme Firefox uses, but it's similar enough that recovering passwords is equally as trivial. Here is the tool for that.

The long and short of it is that any system for storing passwords which doesn't have you using some sort of "master password" to unlock the vault, is storing the password locally in a way which is going to be well known and easy for an attacker to reverse. Technically, hardware solutions like smartcards and YubiKeys can also be used in place of passwords; but, that's a whole different area of discussion. Sadly, when things are really convenient, they are usually also really insecure.