Honestly, aerial approaches aren't the name of Smash 4's game. You can punish with aerials and combat other aerial characters with aerials, but air-to-ground is generally not safe. At least none of the characters I play are designed to do it safely. I've been learning about each character one by one and watching footage (gotta study the game as a commentator), and air-to-ground approaches isn't really spoken about.
There ARE some safe options - like Marth FH fair - but we're not really at the point of utilizing that kind of gameplay yet as, across the board, it's just not the safest thing to do in Smash 4. Keep in mind, we don't have a c-stick and we're playing on a flat tiny controller right now with a pseudo-control-stick. Mechanically, however, this is a noted decrease in the effectiveness of air-to-ground approaches and options in general due to intentional mechanics changes.
You have to focus on footsies, jabs, grabs (grabs are something many newer or lower-skill players don't use enough), and sadly rolls (with some dashes mixed in to change spacing points).
Use aerials when you're both in the air - that's the best utilization for them in Smash 4. That's not even out of the ordinary, because high-skill play usually works like this anyway as metas develop.
This works as a competitive playstyle as you can fake-out aerial follow ups with empty jumps and grabs/jabs/smashes/whatever on landing as there are inevitable landing lag frames for everyone now.
Punishing landings is how I've seen most players dominate, and it seems to be at the forefront in Smash 4 due to landing lag when airdodging (good!) but no real alternative way to safely land in return unlike melee. Character-specific ways of juking landings and landing safely are more important now, and make some of the cast stronger in this current metagame than others.
