I would go so far as to argue it's the entire aspect of the value proposition. Take away decentralization and all you've got is a poorly architected, inefficient, unwieldy PayPal.
The people in this thread understand this value prop, but for a significant portion of crypto investors, the value prop is gains.
It may be true that some casual crypto investors are interested because of the decentralization aspect, but that same user wants a PayPal-like experience. Most are not willing to deal with the complexity of doing it "right", and most of the non-technical people I know who buy crypto do it for the gains, not for the defi.
In effect, this makes decentralization nothing more than a marketing promise, and the reality is exactly what you said - a poorly architected, inefficient, unwieldy PayPal. Sure, this system is capable of much more, and realizing the "true" value prop of decentralization, but that doesn't matter much if users are in it for other reasons.
If users were doing it "right", or for sake of argument, let's say users are forced to do it right, I suspect they would just stop participating, bringing valuation down with them.
The way it's actually used completely destroys that part of its value, but don't let reality get in the way of a good investment opportunity. I think if you set up a coin that doesn't use a distributed ledger, and instead uses an SQL database, you wouldn't get buy-in from the ~tulip~crypto fanatics because it doesn't line up with aforementioned mythos.