It's bad practice sure, but to say that it "completely negates the entire point of two factor authentication" is ignoring the main attack password managers are good at defending against: credential stuffing.
Example: If LinkedIn leaks my password, attackers can't use it to gain access to my Gmail because (thanks to the help of a password manager) I use different passwords for all sites. They also can't use it to gain access to LinkedIn because I have 2FA turned on. Even if my OTPs are saved in my password manager, they would need my master password for that.
And if they have someone's master password, they're probably screwed whether or not they have OTPs in their vault because they likely have credit card numbers, addresses, social security numbers, etc in there too.
If you’re putting all of your OTP codes in your password manager, that completely negates the entire point of two factor authentication.
And sure, maybe you think “well I’m not a high value target anyway, I don’t need to really secure my devices”, how many of you have work-related accounts signed into your devices? Even if you’re just a lowly engineer, I can guarantee you absolutely are a target of sophisticated hacker groups (ironically you may even be more of a target because these groups know that you don’t consider yourself a target and therefor are more lax with your security).