I found this quote from the late Nyingma lama Dilgo Khyentse Rinpoche: "In this decadent age, because of their limited intelligence and lack of determination, people need to practice the Dharma in an essentialized form."
I have heard this elsewhere, that we live in 'degenerate times' - mainly from Tibetan Buddhists. Hindus may say we are in the Kali Yug, a dark age, which is maybe the source of the idea.
There are now commentaries simplifying commentaries made in the past, which in turn were simplifying even older teachings etc. I think in modern times we do need simplified and more 'sexy' texts to spread Buddhadharma. Many Tibetan teachers have published such books, made teachings available online etc. I applaud it, as some of the teachings are simply beyond words.
Now, we can approach this in two ways:
We can regard these simplifications as a replacement for the older more complex texts.
We can see them as an accessible introduction which encourages us to read the older scriptures. I suggest this is what a minority of new Buddhists will do, which leaves them with a very predigested menu.
Now, whilst this may be true for, say, Je Tsongkhapa or Chandrakirti, is it true for Shakyamuni?
Looking at the Pali Canon and early Sanskrit texts, they seem to be fairly easy to follow, especially with a good teacher to hand.
Could it be that the reason we need to simplify teachings is that over time monks have deliberately made their works more and more inaccessible and complex in order to increase their own value?
Or worse, out of ego, could it be that they were dissatisfied with simplicity and wanted to show that they could be as clever and complex in their thinking as the rival sects?
I don't have an answer, but it does seem that over time teachings have become more inaccessible, that cultures have grafted on superfluous beliefs and practices, and that now there is need for a simplification of that complexity.
This may be better achieved, but maybe less fun, by simply going back to examine the Pali canon and early Mahayana scriptures.