来不及爱你 Too late to love you why the phrase 来不及 is translated into too late?
why not use 太迟？ 太迟爱你.
what is the different between them?

and why does 来不及 mean too late in the first place? 


来=come 
不=no 
及=？？


Makes little sense to me.
The break down:


「來」(come ) 
「及」implies 「及時」 (in time) here.
「得」or 「不」 are the two potential particles that indicate " "able , or "unable" 

*You either able or unable to come in time.  That's why they are called potential particles.


In summary:

「來」 (come) 「不」(unable to) 「及」 (in time ) 

「來不及」= unable to come in time = too late

「來不及愛你」= unable to come to love you in time = too late to love you.