Buddhism in the Latter Day is more profound because the times are more severe

"Thus, although their enlightenment may have been the same, from the point of view of the teaching that they propagated, Ashvaghosha and Nagarjuna were superior to Mahakashyapa and Ananda, T’ien-t’ai was superior to Ashvaghosha and Nagarjuna, and Dengyo surpassed T’ien-t’ai. In these latter times, people’s window becomes shallow, while the Buddhist teaching becomes more profound. To give an analogy, a mild illness can be cured with ordinary medicine, but a severe illness requires an elixir. A man who is weak must have strong allies to help him." -- Repaying Debts of Gratitude