I agree more with what you said that someone with disposable income and common sense is better off forgetting about securing their phrase key.
You having a deposal income is good because you can afford to buy Bitcoin with them, but what I don't agree on the bold part of your statement is that common sense can stop your Bitcoin wallet from being hacked.
Well what I mean to say is that ommon sense alone can not stop you from accidental loss or even device loss. Which clearly means that you need to be open to acquire more knowledge while you are accumulating some SATs into your Bitcoin portfolio.
For the fact that we don't store our Bitcoin the same way we save our Fiat currency makes it clear that we should always protect our seed phrase with extremely care, it only takes luck to see your seed phrase or let's say recover your lost wallet, and man lost Bitcoin are done out of carelessness, which is the main reason why common sense alone can not help us secure our wallet more. I guess common sense only comes when you want to buy Bitcoin, either through P2P or any other method of your choice.
Because of this I think that after I better understand how to prepare and learn to secure a phrase key I don't need it anymore.
Everyone honestly need to learn how to protect their seed phrase because the result of a careless investor is regrets. So the best way to avoid regrets is by protecting your wallet from dangers like malware attacks, phishing links, accidental loss, device theft/device loss or hacking, even most times as humans we also make a lot of mistakes because of the inability to develop the mindset of learning.
Even if someone does have Bitcoin learning is definitely no longer necessary for them. And even if they do it's certainly a waste of time that serves no personal benefit.
Everyone needs it, and during the learning process we also need to practice it too by investing and other necessary things that are attached to it, there will be some bunch of mistakes if keep on learning the through theory alone without doing some practice. However, knowledge is never a waste of time because it's very important in the future even though you are not making use of it percently.