Not only is the advent of bookless or largely bookless libraries too large and powerful a change to be forestalled, it also offers too many real advantages for it to be considered a tragedy.

请问老师这里的to be considered a tragedy是不定式还是too...to结构，为什么呢？还是too..to结构的本质就是，动词不定式作目的状语吗？期待老师的解答，谢谢！