Combos work differently in SFV you just have to fiddle around.
Also of note, outside of target combos (the dial-in combos listed in the commands tab) lights will not link in to anything heavier. So a lp or lk will combo into itself, but nothing else typically, except some specials. Ken can cr.lk into a dp for example (or could, dunno what all has been changed). The game seems heavily based on counter hits and crush counters as well. An example being, Gief's St.RH , on a crush it launches and you can combo in to his Ex-Air-SPD thing. I don't know if reg will combo or not, I *think* it's only ex. But point being, crush counters and such open additional opportunities to hurt people.
Also, on the target combos, pay close attention to the moves themselves. I noticed a handful of target combos lead in to a hkd, and several pushed your opponent away a good distance and so.e had 'hopping' moves in them, which on a read could be used to go over low pokes and in to some damage.
I'm not saying they are all useful, many leave me scratching my head too, lol, but some I can see as a 'get off me' or corner push move, or, like I said, as a way to punish a sweep under certain circumstances.
I like sf V but I'm reserving final judgement for release, as it does feel a little bland. Footsies are great and fun, but I would like more links and more options, or after a bit matches will be the exact same one or two pokes into the exact same combo (because characters only have like one).
That's just my VERY preliminary opinion, the game has a lot of room and time to grow and I hope it does. It's completely possible that I'm totally missing the depth of PLAY here and I hope I am, but right now I'm seeing great mental depth yes, but not so much from the game system's stand point.