This is an interesting viewpoint, but for me misses an essential point - the speed of progress is often such that the points above don't actually matter for the vast majority of people. Built-in obsolence either done deliberately or through cost-cutting doesn't matter if you will replace the device before the time of the obsolence.
I like good quality long lasting things. I like my property to be no more mortal than I am. Why should I have to suffer things being inadequately made and failing on me? Why should anyone?
But if, say, 90% of people will replace the item anyway before it fails, then they haven't suffered it. This is the point I'm making - items that people are likely to keep ages still ARE made well. Think about cars - they're much, much more reliable than they used to be, esp. at the lower end of the market, and require much, much less maintenance. Why? Because people keep them for years and years and so their reliability is a major factor on purchase. So it's not as if we don't value reliability and quality in certain areas.
But with ephemera (and for most people, a computer, a phone, even a toaster, etc are ephemera), the long-term reliability isn't an issue on purchase because they're likely to buy an upgrade before long-term reliability comes into question. In that situation, ensuring long-term reliability becomes an expense the buyer has no interest in paying for, and rightly so.
Leaving aside business/profit concerns, even if one were to hypothetically mandate all items lasted 10 years, the effect would be that the cost of the items would increase, due to the need to improve component/build quality, and so the number of people that could afford them would drop.
This strikes me as unfair. I feel that the more people that can afford the latest trinket they can enjoy, the better. And this consumerist principle is greatly aided by cutting costs, lowering the unit price of an item. As long as the effect of cuts isn't perceived as deleterious by the vast majority of purchasers (either because they'll upgrade before failure, or the unit price is so low as to make replacement pain-free), in my book it counts as "no harm, no foul".
Where it goes wrong, and manufacturers overdo it, the negative publicity they suffer (leading eventually to revenue loss) should equilibrate the market, provided they're not indulging in anti-competitive/abusive practices to distort the marketplace of course.
I do appreciate that this is a fairly strong capitalist/consumerist/aspirational worldview though, so I don't actually expect you do agree with the principles herein, which clearly differ quite strongly from your own value system. Just thought I'd state my thoughts a bit more elaborately.