I read most of Nietzsche’s works in the original and the idea that it can be reduced to a sentence is just wow. What I find most damaging about this (quite contemporary) attitude is the consequences: People read your (or a similar) statement and think “he studied it and concludes that Nietzsche is just about achieving greatness - no need to bother.”
Actually, if Nietzsche was so great he should have realized it himself and instead of books he should have published a poster.
The mind is stubborn and stays where it is unless it is forced to move by insight and experience. A reductionist attitude towards other worlds/systems/teachings simply lets the mind stay where it is and nothing changes.
If a mind is otherwise well prepared, yes, Buddhism could be reduced to the 4NT. But really, the 4NT are crystal clear in their definitions - why bother with any further Buddhist studies?