Your use of dair in Melee can be wise, but I'm more-so surprised how you're not complaining about the removal of shine spike. In Sm4sh, almost everyone has a free recovery (aside from Little Mac) and there's no edgehogging, so I personally see no reason to not go out for the kill. If you stay on stage and play safe, the player will most likely take ledge, and do a normal getup which is really hard to punish. I'd rather take my chances offstage. If they're trying to recover high, RAR bair or an up-air works wonders. If they're going for ledge I'll try to stick out a nair or a bair to clip them. If I'm feeling particularly confident, I'll even fair my opponent offstage. One time I was fighting a really good Falcon and gimped him with an offstage, fast-fallen fair. Granted, he narrowly hit the blast zone before me, but it was still epic.
If you have custom moves, the charge laser or wolf flash are also good options. The charge laser can force them to recover high/low. Also I've been able to combo down-throw to Wolf Flash and get the meteor hitbox.