Ok, here goes:
-Small volume knobs (Goldstar TSR-800, Sharp GF-700)
-Fake speaker "bolts" under the grill or even at plain sight
-Small woofers on huge boxes
-Separate eject button (makes quick side changes more of a hassle)
-Some controls on top, that could easily be installed on the front
-Piezo tweeters without any engineering/crossovers (GF-575 seems to be a rare example of piezos done right)
-Underpowered amps (Philips D8444)
-Bass ports that are too small and start suffocating at high volume (Hitachi CX-W700, Philips AW7694)
-Flimsy plastic feet
-Flimsy antennas
-Flimsy carry handles (Philips)
-Stereo "WIDE" that makes the thing sound like its screaming at you
> "Surround" nonsense (CX-W700, 3D80, AW7694).
> Same effect as "WIDE", but with the name SURROUND
>SURROUND labeling and options that make no sense and have nothing to do with Surround sound (3 or 4 channels)
-DIN inputs that work only as record inputs without the recorded sound coming through the speakers
-Bad shielding on top controls that let dust and grime in (3D80)
-Bad design of power section that makes a lot of hum in a silent environment
-Bad balance at lowest volumes
-Loud cassette mechanism
-Tape doors that misalign the tape (Philips D8634 Mark II)
-Torx screws on azimuth adjustment (Philips)
-Mechanic deck controls that are swiweling on a radius that makes them hard to press
-Mechanic deck controls that are too soft to press and go bollocks when doing fast fwd/rew searches
-PMPO or other maximum power figures (20W, 40W, 50W...100W...200W!!!)
-Hard to service insides (messy, no removable connectors, just soldered wires etc.) (Siemens Club 745, Sanyo M9990)
-Big speaker grills, small speakers
-Grill that are probably impossible to remove without hacking (molten/glued on place)
-Molding around speaker that looks like a fat modern upper surround, but is fake
-Adhesive tape or metal plates in the place of piezos (probably made no difference, but still)
Aging related:
-Stiffened upper suspensions on woofers
-Yellow tint on gray
-Hazed tuner windows
-Molten rubber
-Hardened rubber
-Bad function switches
-Bad tuners
-Dust and grime under the grills
-Weird smells
-etc.