They most certainly are not. Remember: Baijiu is not a brand of alcohol; it is a type of spirit. So this is like asking: are all vodkas the same? are all whiskeys the same?
That being said, as a type of spirit, Baijius all share certain characteristics, the same way that all vodkas or all whiskeys share certain characteristics. For instance, all Baijius are clear in color and consist of around 50% alcohol. Many Baijius are distilled from sorghum, although by no means all; some Baijius are even brewed with fruit!
Baijius vary greatly in taste, price, cultural history, and recommended usage. For instance, Shui Jing Fang (Wellbay) Baijiu is made at the oldest distillery in China, has been designated “The Top Chinese Luxury Brand”, and has a refreshing floral taste. On the other hand, Kweichow Moutai (Feitian) Baijiu is the official national liquor of China, the official state banquet wine for Chinese dignitaries and government officials, and has an earthy, silky taste with spicy notes and a long-lingering fragrance.