This is a good opportunity to apply the "reversal test": you say the status quo is better than an envisaged alternative, so let's see how it looks if that alternative is the status quo and someone proposes to switch to what we have now.

So: Imagine a world in which people (let's say) stay at 25-year-old health until the age of about 90, and then die quickly. And suppose, in this world, that someone comes along and says: "Hey, I've had this great idea. You know how sometimes it can be difficult for young people to be successful because older people are more effective? Well, I know what we can do about it. I've got this stuff we can put in the water, and what it'll do is make everyone degenerate with age, so that they lose energy and brain function and strength and so on. Most people will have stopped paid work entirely by the time they're 70. A lot of people will find themselves practically unemployable before they're even 60. What's not to like?"

I can't imagine that the response would be very positive.