Bismillah,
Asalamu Alaykom,
Delaying Salah (unless delaying it would cause it to become qada) isn't haram. Yes, it is highly recommend for one to pray on time and this would gain them the maximum reward. One should think of it in the way that each minute that goes by where Salah is delayed, is one's reward decreasing.
May Allah make us among those who are able to regularly pray our Salah on time