I'm pretty sure that earwax per se doesn't cause deafness. However, wax will prevent sound penetrating to the ear and give the symptoms of mild deafness. Perhaps if the wax is left in for a long time and infection occurs behind the wax this may affect hearing.
However, age is definitely the biggest cause of hearing loss. 1 in 6 people have a hearing loss of some kind (all ages). But this increases to 1 in 4 in people over age 50 and 3 in 4 for people aged over 75.
The kind of hearing loss is sensorineural which means the hair cells in the cochlea die away. A hearing aid only has limited capability to help because when the hair cells die, the connection from these cells to the hearing nerve is gone. So no matter how loud the sound you still can't hear it. Most often the high frequency cells die first so slowly all these sounds cannot be heard.