Seems like once the novelty of these buildings wears off, and once developers start figuring out how to build smaller, more window-y "missing middle"-type buildings (which seems like it might be the new trend), folks won't want to have to pay a premium only to then have no windows and/or less privacy (via French doors, sliding curtains, low walls, etc.). At the very least i doubt they'll be able to keep marketing these 1BR + windowless dens as 2BRs, or studios as 1BRs, and there will be some kind of consequences to that.
Having worked on dozens of these, I've got to chime in here.
Putting your own desires and opinions aside, the EVIDENCE (built projects) is clear - these buildings lease up and get sold. The market for multi-family rental is strong and it is off the charts in desirable cities with strong economies (Minneapolis). The projects are in SUCH high demand from investors that many of them sell before they have left "the drawing board." Do you realize how strong that is as an investment? I obviously don't understand your concerns regarding the long-term viability but when these projects get sold before they are even built, do you understand that they are being sold for large profits? No property owner is losing sleep worrying about how to make the mortgage, they are too busy spending the cash that is flowing from rental income (the reason that they invested in the first place).
I'll get back to the units in a minute but you clearly don't understand what are driving these projects:
1. Location - neighborhood amenities (restaurants, night life, biking trails, rivers, creeks, cafes, etc)
2. Amenities - pools, pool decks, lawn bowling, fitness rooms, yoga, "private" coffee shops, concierge service, bike maintenance areas, dog runs
3. "Common space" within units - "open plan" living/kitchen/dining
4-56. Others
57. Bedrooms
To put it more succinctly, the preference of "public" function over "private" function is at work at each scale. The "public" function is BY FAR the driver in each case. I've been in countless meetings with development teams and I've heard it dozens of times, "There are only two things going on in bedrooms and they tend to happen in the dark."
RBY had an excellent response to the longevity of new construction versus old construction. I'd like to accentuate that it is easy to build an uninsulated wall that "breathes" moisture back and forth all day and night through the wall assembly and then use massive amounts of energy to pump warm air in (or cool air) for human comfort. Claiming that building this way is superior to new construction is just ignorant - it is not sustainable and therefore the "technology" involved isn't something linear that can be leveraged by just adding insulation.
Units and a few important distinctions:
Studio: NO bedroom enclosure of any kind
Alcove: Bedroom enclosure that does not have a window to the outside
Bedroom: Window
Units Widths: Studios (can be 16-20' wide), Alcove (~18-22' wide) 1 Bedroom (~23+) which means a 12'(ish) living room and 11'(ish) bedroom that is "on the glass".
Marketing is what it is and these things can have whatever name they like but as unit sizes increase or bedrooms get enclosed or get windows, cost goes up. Anyone looking at units will have to weigh the importance of a bedroom window, a bedroom enclosure or watching TV from a bed. Anyone who rents a unit listed as a "1 bedroom" without comparing to other "1 bedrooms" is ignorant and/or lazy. I'd wager that these people are in the minority and understand that terminology can vary but at the end of the day, it's easy to see whether or not a bedroom is enclosed or not - it's not a "bait and switch" or false advertising. Management companies could call the units "Flarglesonss", if they aren't compared to other dwelling units, it doesn't matter what they are called.
Potential tenants aren't blind-folded when they walk through the units, they can see how the bedrooms are configured. When I first worked on these projects, the "alcove" type of bedroom (interior to the unit) comprised a smaller percentage of the overall unit count but that unit type has continued to increase over the last 6-8 years. It is handy for the developer that the desirability of alcoves have increased as the density tends to drive the profits up but if these units weren't being leased (no demand), they wouldn't build them (more of them) on the next project. The fact that alcove enclosures may not reach full height has nothing to do with code and everything to do with borrowed light. Borrowed light is also why alcoves are often designed with large sliding barn doors and/or transom windows or sandblasted glass facing the living space. These are design innovations that are a response to the depth of a unit and the desire to bring as much natural light as possible into a unit.
Just because you are disinclined to rent such a unit it doesn't mean that others are and the market does not support your inclinations. Many people can't live without a bathroom window - in an interior unit of a multi-family project these are basically impossible. People with these needs are best served in a single family home. The needs of such people are not even a consideration for developers of MFH.
Lastly, the "longevity" of buildings is driven by the code. There is very little incentive for a developer to build anything above "code minimum." The buildings are designed to meet code and are inspected at every step to insure that they are built according to the drawings. The structural engineering is done to a factor of safety that is very conservative. There is even language in the code regarding the "deflection" (bounciness) of a floor assembly. Empirically, I've lived in and spent time in many a building that was not built with floor joists that were at/near their limits for structural capacity and walking across the floor felt like walking across a trampoline. 60's/70's era "Garden Apartments" that are all over south Minneapolis were not built to be 100 year buildings either and surely their "amenities" within the units have not withstood the test of time. The owners of such buildings have had to make a choice: do nothing and keep rents relatively low (yay affordability) OR spend money, renovate and increase rents to stay competitive. So, the phenomenon of maintenance/style changes/desirability that you are so concerned about is really no concern at all, the owners of these new buildings will be faced with the same prospects 20-40 years from now. Romantic notions about "100 year buildings" and "they don't build them like they used to" are just nostalgia with no basis in reality.