This is generally very good advice in that you should be sure you've done your homework on your needs and wants and the alternatives before committing to any purchase. I'll just point out a few caveats:
1.) Direct-from-owner rentals from Redweek, TUG, eBay, AirB&B, etc. can indeed often be rented for maintenance fee costs or less. (But not always in high demand locations/high seasons, those sometimes go for double the maintenance fee.) But these owner-based rentals come with limited to no cancellation rights and additional risk because you are dealing direct with an owner not a large company with many resources behind them. There are scammers out there in the owner rental market. But if you are willing to live with those limitations and risks, these kinds of rentals can offer great savings over rentals from mainstream rental markets like Marriott.com, Expedia, Orbitz, etc., and may be an alternative to ownership for some people.
2.) The financial losses on selling a timeshare are primarily realized when you've bought your ownership directly from the developer at their much higher prices. If you buy resale and don't overpay, your "losses" can be minimized. But I've always thought this to be somewhat of an illusory argument. Most things you buy are worth less than what you paid when you try to sell. Cars, even used cars, can rarely be sold for what you paid. Look at all the resale items on eBay, Craigslist, etc. - all are being sold at a "loss". So why should people be concerned about recovering their initial investment on a timeshare when that doesn't concern them when buying a car? The value of a timeshare - like a car - is in the use. A TIMESHARE IS NOT INVESTMENT PROPERTY. It is something to use and enjoy and then when you sell, get whatever you can based on the market value. I really don't understand the logic of why someone would ever expect to buy a timeshare and then expect to be able to "recover their initial investment plus yearly fees." A timeshare is not the same as regular real estate.
3.) Yes, it is correct to consider that your interests may change over time, but that doesn't mean you shouldn't buy. We've owned timeshares of one kind or another since 1999. Back then we had an infant and a pre-schooler. Now we have two college students. And just because you own a timeshare doesn't mean that restricts you to only timeshare vacations. The first timeshare we bought in 1999 worked well for 10-15 years, but when we decided we needed more flexibility than a traditional weeks-based ownership offered, we sold it and bought into Marriott's new points product. Now we are no longer locked in to 7-night stays and can use our ownership for long weekends and other shorter stays. And throughout our 18 years of ownership, we've taken other trips not involving our ownership - things like a multi-city trip to California using hotels, a Disney Caribbean cruise, etc. My wife and I are planning a Mediterranean Cruise for next year. Timeshare can function well as one piece of a travel strategy, but rarely can it serve 100%.
The most important thing is to do your homework and figure out what works for YOU.