Bitwarden currently generates 14 length random passwords by default. For comparison, KeepassXC generates 20 length and 1Password desktop applications generate 30 length and 20 length for browser extensions by default.
Yes, users can change password length manually, but I think it’s better if Bitwarden generates long password by default.
If the user imposes no restrictions on character sets used for generation, then a 14-character random password has 86 bits of entropy. That level of entropy provides more than sufficient resistance against brute-force password cracking for the vast majority of applications, so there is nothing wrong with having the default set to 14 characters. In contrast, because there are many websites that impose password length limits, increasing the default password length will increase the probability that generated passwords will be rejected; this would be an argument against increasing the default password length.
The only variation of this idea that would make sense (IMO), would be to increase the minimum password limit depending on what character sets have been enabled. For example, to maintain a reasonable level of entropy (say, 72 bits), if the choosing to generate a password consisting only of special characters (3 bits of entropy per character), then the minimum password length should be 24 characters; for uppercase alphanumeric passwords without “ambiguous characters” (5 bits of entropy per character), a 16-character limit could be imposed, etc.