Not sure about new cars my current car is now 10 years old
(xantia) but i can still manage to change gear, up and down without clutch it does take a bit practise but if your carefull with gear stick you can feel when it's ready to slide in
. It's all about getting the moving parts inside the gearbox rotating at the same speed as the engine is rotating.
Not sure if this is still posiable with gearboxes with straight cut gears used in race cars, i believe (I'm no expert)
.