Ok...? It's still a more technical game. I could write a 100page essay of the technical aspects and tools at your disposal.
With enough practice I was able to get 1frame links, it took a long time no lie, but I was able to do some in SSFIV
It's been 10 years of playing SSBM for me and I still can't do everything Fox can do.
Please understand I'm talking about Fox. As he's the only one who is way too difficult to use all tools with. It's been 12+ years of SSBM and the pros still can't use him to his full potential. (And by that I mean his tools)
most other characters are not 1 frame specific minus perhaps samus and a few edge instances.
Give me a second and I'll make an epic post about SSBM's depth. so you can see it from my eyes.
Here is just one example for now.
In Street fighter, when you "block" you essentially just block high/low/Parry. You slide back a little bit on each hit as to not be stuck in infinite pressure. You got your lows/overheads/focus parry ect ect.
SSBM has low's and high's and mid's as well except they work different. a shield aimed in any direction covers all mid hits. A shield aimed down your head will get poked out by a high hit, and if you aim your shield high you'll get hit by a low poke. ok same stuff. But SSBM has has this in their shield play.
They can aim their shield TOWARD you. So your move hits the shield sooner, giving them a bigger window to punish you before you can do another move/shield yourself. SSFIV can't aim their block At your to make a move hit sooner. As once the move hits a shield it no long has a hit box. You can also aim your shield away, to make it so a move hits late, to try and make your opponent miss time their L-cancel. (refers to lag cancel, as any aerial when timed just right the lag can be cut by 50%) if a person hits a shield late their timing might be off because when an attack hits a shield they hit the ground at different timings.
now for the push back. the harder and farther you hold in the shield button. The heavier the shield, and the less shield stun you recieve but it's a smaller bubble easier to poke you, but you don't slide away far while under pressure.
If you light shield, you get more shield stun but you slide back alot farther getting you out of pressure, but you most likely won't get a counter attack because of increased shield stun. (bigger bubble) to light shield you have to BARELY hold down the block button. The game has a lot of pressure sensitive aspects.
All of this do-able from the defendants side.
The glorious thing about SSBM is you are doing alot of work, even while defending.
While you are pressured, You are also holding down on C-stick while in sheild stun so incase you are poked. You are ASDI'ing down (auto smash Directional Influence down). To ground your character so they don't go flying for a combo if they are hit. And if they are HIT and you call it out. You can hit L- and tech off the ground before you even leave it.
And once you are knocked into the air, You can still control your character while you're being combo'd through directional influence, where you can choose if you go higher, fly not as far from your opponent, fly farther away, or fly close to the ground. all of which to combo your opponent needs to read/react.
In street fighter... when I'm blocking.. all I'm ever doing is holding back or down-back. and waiting for an opening for me to counter poke/attack. Or I focus parry a move.
As far as crossups though SSBM has none, but ssbm isn't stuck in facing one direction. So it's a depth in itself when in SSBM your character is more advantaged when facing a certain direction. for instance Donkey kong is incredibly good out of shield when your behind him. But if you Cross up your attacks and stay infront of him. He can't do much.
SSBM ont he parry side has powershielding if you shield just as you are hit, You get 0 frames of lag when dropping your shield. But the precision to land a powershield is a 1-2 frame timing of the hit connecting.
Fox can actually do HIGHER apm than this, but since we're only humans this will have to do.