Are tyres >10 yr old unsafe ?

www.aa1car.com/library/tire_expire.htm
I have a Michelin 205/65R15 94H MXV8 made in '02 wk 2 :
in 5-07 i.e.<5½ yr old but already ½ of its rubber had
cracked & could not hold nitrogen. 2 other Michelin 195/65
R15 ( ~5 yr old ) I had, likewise had cracky rubber, though
could still hold nitrogen.
I have a Dunlop Jcinq 185/70R13 made in '95 wk 20 : its
rubber looks fine, & still can hold nitrogen quite well.
I think this question depends on the brand of a tyre.