All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
We have already issued Fataawa 90491, 86669 and 85129 clarifying that what is considered in determining the beginning of the month is the actual sighting of the crescent or by completing the month of Sha'baan 30 days as there are many authentic narrations proving this.
Undoubtedly, it is an innovation to claim that the nation was not able (since 1400 years) to understand the verse of Allaah and the Prophetic narration, which you referred to in the question. The nation, all perfect praise be to Allaah, understood from the verse that "whoever sights the month," means he is present during the month of Ramadan, then he is obliged to observe the fast as long as he is resident (not travelling) and in good health (not sick).
The saying of Prophet : "Observe the fasting according to the sighting of the crescent (of the month of Ramadan)", refers to really seeing it by one's own eyes, and not by calculating it astrologically, and this is what the wording obviously means, as calculation is not called sighting. Therefore, whoever says that the meaning of sighting in the narration refers to astrological calculation, is required to provide evidence as he is taking the meaning of the word out of its proper context. What proves that the Prophet meant the sighting by one's own eyes is his saying: "We are an illiterate nation; we can neither write nor know how to calculate. The month is like this and this" (raising his fingers to indicate that it is sometimes of 29 days and other times of 30 days). [Al-Bukhari and Muslim]
Therefore, whoever says this, is required to repent to Allaah and whoever has religious knowledge should clarify to him the truth with wisdom and soft words. Then, if he repents, this is what is required, but if insists on his statement after establishing the evidence against him, then he is an innovator and he innovated something new for the nation.
Allaah Knows best.