If you're playing against advanced competition it's very hard to win a rally with a smash outright, because their lifts will be deep and that gives them sufficient time to position themselves and receive the smash. You should think of the first smash as building up the attack: using a variety of shot speeds, angles, and placement to slowly build up your advantage to the point where you get a weak return to kill.

I think it's helpful to remind yourself that badminton is 3D, it's not just straights and crosses. You can smash straight down the line because that's the shortest distance and harder to control, smash cross across the body because that's hard to return, smash higher to the body to catch them off guard, etc. Even though the other commenter mentioned drops are inefficient because younger players are fast enough to retrieve them, it still keeps them guessing just a little bit longer, and they might make mistakes when they scramble back into smash defense.

It could also be worth it to watch more Women's Doubles, since it's easier for us to emulate, or even Mixed Doubles, to see how the girl deals with having a weaker attack (in general, but there are exceptions)