Edward Conze (1904-1979) was a notable translator of Eastern texts into English, as well as the author of books such as Buddhist Meditation, Buddhism, etc.
Here are some quotations from this posthumously published 1980 book (NOTE: page numbers refer to the 154-page 1993 Oneworld edition):
"The division of Buddhist history into periods of 500 years does not only agree with the facts, but it is mentioned in many Buddhist writings dating from the beginning of the Christian era. These five periods of 500 years are enumerated as marking the continued degradation of the doctrine." (Pg. 5)
"Some modern European books abound in confident assertions about what the Buddha Himself has personally taught. They are all mere guesswork. The 'original gospel' is beyond our ken now. The farthest we can get back in time is the period when the community split up into separate sects." (Pg. 9)
"Little attempt was made to weave all these stories into one consecutive biography (of Buddha). At present we are not in a position to decide which ones of them are trustworthy historical information and which ones are the pious inventions of a later age." (Pg. 20-21)
"Our Hinayana sources ... were practically incredulous of all these innovations (by the Mahayana sect) and they refused to take seriously the claim that the new Mahayana works gave the Buddha's actual words. In fact they rejected these works as just so many 'concoctions' and unworthy of serious consideration." (Pg. 54)
"Unlike the early Mahayanists, the Tantric authors no longer link their scriptures with Sakymuni, but frankly assign them to some mythical Buddha who is said to have preached them at some remote and distant past." (Pg. 77)
"What had of course happened was that in the course of 1,700 years of co-existence the Hindus had taken over a great deal from the Buddhists and the Buddhists likewise from the Hindus. In consequence the division between them had increasingly diminished and it was no great thing for a Buddhist to be absorbed into the largely Buddhified Hindu fold." (Pg. 109)
"In Japan our industrial age has put a premium on those sects, Zen, Shin and Nichiren, which have most radically departed from tradition." (Pg. 143)