I think it is true. The less Apple puts on the inside, the more people are going to have to put on the outside.
Ever since the original Mac - and
certainly since the original iMac, appearance
has been an important part of Apple design philosophy. The issue is where to strike the balance, both in individual models and across the range. Jobs oversaw some of the most sealed-in devices ever produced but he
also presided over machines like the G3 tower and "cheesegrater" that went the extra mile to provide easy, internal expansion. Balance.
My 2017 MPB is a fine example of this.
...and the problem there is that nuApple got the range wrong: as extensions of the 12" MacBook range - for users who
want ultimate portability over versatility - they're fine (except for keyboard reliability). As the
only choice for Pros/Enthusiasts/Power users who want a mobile workstation, they suck.
In terms of the iMac, the only thing really lost in the switch from the 2010 to the current "tapered" design were the optical drive and FireWire. Whether these were "obsolete" when dropped in 2012 is a matter of opinion but I would say that they were firmly "legacy" at the time in terms of their use by new products (unlike USB-A today - I'm still buying USB-A devices with no USB-C alternative and which would have nothing to gain from using USB-C). Also, in my experience, those slimline, slot-loading optical drives had a half-life of about 6 months so I'd
rather have a cheap, external one when needed. Even in terms of "fixability" - even with the old system of magnets, getting in to a 2010 iMac was not for the faint-hearted, needed special tools (suction cups) and ran the risk of getting dust between the screen and glass. Now you need a pizza-cutter and a new set of adhesive tape, but the glass is laminated to the screen so no dust (giving less glare, too). Meh.
The big iMac issue, IMHO, is the lack of front-accessible USB and SD card slots. However, the side-mounted solution (as per the SD and optical in the 2010 iMac) stops looking like a good idea as soon as you think about dual-display setups. Having a hub sitting on the pedestal is probably the sensible solution (can we have some TB3/USB-C docks
designed for iMac, please - i.e. lots of USB including front-facing and
powered by the computer using USB-C power delivery rather than with a huge power brick designed to
charge a computer?)
There does seem to be an issue with the current top i7 model and cooling - now, I've got one of those and my experience is that yes, it is quite loud by modern standards when fully loaded but that it wouldn't be a deal-breaker
unless you wanted to use it in a recording studio... which is a thing. However, I think that issue will probably go away if Apple release an 8th gen 6 core i5 option.
I read only yesterday on MacRumors of someone complaining about slow Bootcamp and the advice was to add an external SSD because the internal drive isn't good enough.
To be fair, I believe that is because Bootcamp/Windows don't support the SSD portion of Fusion Drive & therefore only run at mechanical HD speeds. Friends don't let friends buy iMacs with spinning rust in them.
Thing is - having external boxes and dongles is much less of an issue with a desktop than a laptop where
you have to carry them around. My bulk storage/backup is on a NAS tucked under the desk, the internal SSD is big enough for fast access to work-in-progress and the iMac already has more i/o than you'd get in a laptop, so an external hub is very much expansion rather than necessity.
For those who need
more then the problem does not lie with the iMac but with the lack of a Mac Pro, and Apple's apparent determination to make that some sort of exotic, expensively-developed small-form-factor gimmick based on their second-guessing of pro workflows - rather than just calling Foxconn and have them deliver a container-load of PC mini-towers with MacOS-compatible components and nice aluminium enclosures by the end of the month.