I suspect that the thing that will cause a lot of modern cars will be from glitches in the software, sensors and electronics. Some of these will just be annoying, but some will be an MOT failure.
I've got a 2012 Mondeo which is fine mechanically, but has issues with the electronic locking on a rear door (probably from water damage to the wiring), and recently had the immobiliser come on, which meant being recovered to a dealer, where they a replaced the ignition switch and transponder.
I was thinking of getting a KIA Niro and read some forums, with people grumbling about the
Forward Collision-Avoidance Assistance. Some of those might be hardware and software issues that will get fixed in time, as its still in the 7 year warranty, but its a worry for the long term.