A decline is ALWAYS relative to something, otherwise it wouldn't make sense. So what is it really that you mean?
Intel used to be the undisputed leader both on CPU design and production process. Those positions are both lost, Intel also always used to have huge profits, but has had deficits lately, that used to be absolutely unheard of. They have lost both their economic and technological lead and they have lost marketshare, So how is that not a decline by every measure?