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If the news needed to sell a quality product in and of itself, yes, it would be constrained by the need to be profitable. And there would be pressure to cut corners, just as is true of building cars or furniture. But there's a poitn where you're selling a dysfunctinal product, and if the only reason you're building is to sell, and dysfunctional products don't sell, you'll be forced to put in some minimum.
I've got some recent first-hand experience with this, as it happens. My work overseas for the past several years has been in nurturing independent media in post-conflict countries. In addition to developing infrastructure, reporting/editing/production skills and judgment, and appropriate processes, there's also the need for outlets to be sustainable (i.e. financially independent, as well as editorially). That's written into the various financing instruments for those outlets.
Even in places where costs are not high, this turns out to be very difficult to do. No news agency in the world, for example, even covers the cost of their news production without a combination of subsidies and separate information products (Bloomberg is an interesting hybrid case, but the rule still holds). Downstream, individual outlets generally lack the resources to do serious coverage of their own, and rely on content wholesalers (like news agencies). What resources they do possess go into what we would call features ... soft features, not news features. The money to pay the bills, in other words, comes from also being in a business other than the news.
The incentives to cut costs and demean the quality of coverage are everywhere. At the margins it's easier to rewrite wire copy and do ten stories badly than one story well. Investigate or enterprise reporting is extremely costly, and in the absence of other incentives (Pulitzers that perform a rearguard defense of the outlets' reputation and staunch some circulation-bleeding) it's an obvious place to cut.
Even in the absence of big media consolidation (or big media, for that matter), the need for sponsorship, if only for cash flow, is extreme and compromises coverage. A few threads back, I cited the World Bank study of (highly concentrated) media ownership in 90+ countries that showed how this affects coverage. Nor does it get better with state ownership; the correlation with poor outcomes was similar.
(FWIW, the national news agency we started in Afghanistan is almost break-even with a combination of subscriptions, special feeds/collections for big subscribers, periodic special reports sponsored by UN agencies about health or agriculture, wholesaling news and business information to an all-Asia aggregator, some grants from aid organizations, and private fundraising ... some by my wife and I here in the states. And the guy who has to manage all this is also the editor in chief, a very good journalist who also reads and critiques every story ... and who just turned 32.)
This is not to let our media goliaths off the hook, just to add context to the question of what to do about them, if they can't be profitable on their own and can't perform their essential functions as currently configured.