In many ways, your 3rd Strike footsie skills will be useful in that you have to always be aware that single hits from pokes can turn into big damage – it’s just that:
Chars have many more good options for approach in Marvel games, because there are many more options for movement in general. As a result, people rarely walk back and forth out of sweep range in an attempt to bait their opponent – they simply approach from new angle after new angle. The chars with a triangle jump (8-way dash) have near-instant overheads for instance. Other characters utilize raw speed (X-23, Chun), teleports (Phoenix, Wesker), flight (Storm, Trish, Sentinel, Phoenix), or teleports to help create methods of approaching.
Chars can string together many more normal moves. It’s no longer a world of just normal --> special --> super.
Because it’s a tag team match, often your assists are just as important as your point character. Assists open up more avenues of approach (see #1) by covering space horizontally (fireball assist, like Ryu’s), locking your oppoents in place (direct assists, such as Chun’s Lightning Legs), or by otherwise claiming space in some fashion (Trish’s traps).
A common mistake new players make is to get really good with a point character without learning how to integrate them into a cohesive team. This can be difficult to realize, because if you’re proficient enough with a character or two, you don’t have to really utilize the team – you just have to throw your 2nd character in there when the first one dies.
My current team is Spencer, X-23, Trish. My usual goal is to put either Spencer or X-23 on point (based on matchup of their point char / whoever is out at the time), and to utilize Trish’s Hopscotch assist to protect the space directly in front of me. If Spencer is out, then I prefer to pull my opponents onto the trap using his bionic arm, allowing me to go into a devastating air combo – assuming I have a super meter, I will almost always tag in X-23 in midair at the end of Spencer’s combo, take my enemy to the ground, cancel into X-23’s super, and DHC back into Spencer’s Bionic Lancer.
That puts my secondary char (X-23) in for a minute so I can utilize her ability to extend the combo, and then puts Spencer safely back into the fight (which is the real benefit of the DHC here – bonus damage is secondary) so I can hope to do something similar again on the next character.
Most teams will have a primary point char, a secondary point char that either works well in specific situations or counters specific characters, and a tertiary character that is essentially only chosen for an assist (though you have to be able to hold your own on point with this character in an emergency situation).
TL;DR: Utilize your assists to create angles of approach that wouldn’t otherwise exist. This is the most basic difference between SF and Marvel games.