Translation:He is too young to understand the consequences.
The sentence would not work without til, although I can't exactly explain why.
The construction always works like "for tillægsord til at..."
In this case, 'for' means 'too'.
Han er for grim til hende (He is too ugly for her)
Hun er for dum til at blive direktør (She is too stupid to become a CEO)
Jeg er for ung til at gå på pension (I am too young to go on retirement)
Hun er for god til ham (She is too good for him)
I find it helps to think in Shakespearean English when thinking about Danish constructions, after all Danish is closely related to Old English! And old-fashioned English used 'for to' in the same way as Danish uses 'til at'. For example, 'he went out for to see'. When you think of it like that, the 'til at' construction feels like it makes more sense, to me at least, and it means 'til' can usually be translated 'for'.