we should probably start distinguishing between "traditional paper wallets" where users print out a private key using a popular browser-based software and "paper wallets as seed phrases written down". both should be generated offline but the former is much less secure.
I wouldn't call one of them less secure per se.
Paper wallets where the private key (or seed) is generated on an online computer are generally more secure than private keys (or a seed) generated from a downloaded website. Still, both isn't ideal.
However, a properly generated paper wallet has to be generated completely offline. And preferably without any javascript.
Using the RNG from your OS is one of the best way to generate a paper wallet (regardless whether you want to store a single private key or a mnemonic code). A good and reputable wallet can easily be used to do so (e.g. electrum).