My guess would be. TC is for Mac, for this purpose, It's OK at the moment.
1) Silent file corruption is almost unavoidable.
2) Disk failure cannot be avoided, but lost data can be solved by have 2 TC or more (yes, they want you to buy more). In fact, that works quite well, the OS will automatically swap between TCs on each backup.
3) iPhone's backup is made via iTunes, so, eventually it's backup to TC indirectly.
The current TC has Wi-fi ac, 3T HDD. Except cMP user, no Mac need more than 3T backup space (according to Apple's logic). And the Mac Pro user should have their own expensive backup solution anyway, Apple never care about this market.
So, for me, even though I love to see that Apple at least give a silent update to TC (e.g. 4T or even larger HDD), but it seems this will not happen until the iMac has 4T HDD option officially.
TBH, I was a dual TC user. And now, I simply use 1 3T TC to backup the important files, which able to keep different versions for easy recovery. And then just clone my data to another external HDDs every night to have the system snapshot. IMO, TC is only good for recover files, not good to recover system, and the worst is TC that is not bootable. And now, I have my cloned HDD every night, if anything goes wrong on my primary SSD, I can simply boot from the backup HDD and at least have a functioning computer to work with.
I'd try to recover about 2T of data from TC (whole system recovery), it cost more than a day, really crazy slow. For a system that has only 128G SSD, TC may be a very good solution. But when the file size getting larger and larger, TC is far too slow for the job (regardless the network speed, in my own test, TC can only read / write at around 30MB/s max).