ME2 Adept is more nuanced than the other classes, I suppose that is the best way that I could attempt to summarize it.
You don't really have any single power that is hands down better than the other powers, they are all somewhat situational. The game also doesn't really make it clear what each power necessarily is most useful for. It is like "Throw throws." "Singularity lifts stuff." "Pull lifts stuff." "Warp damages stuff."
Engineer also has powers that are fairly situational, but it is pretty clear what everything does. Incinerate damages armor, Overload damages shield, Drone floats around making noises.
Since you don't have a single power that is a lot better than the others, it takes a little while to level up so that you have all the bases covered. Soldier gets to maxed ARush and is practically done leveling. Sentinel or Vanguard are sort of the same way.
The good news is that Adept has very high synergy with the other squadmates, which is not necessarily the case with some classes. Soldier doesn't really have much synergy with anybody unless you consider just giving a squaddie Cryo Ammo synergy. To an extent this is true for Vanguard and Infiltrator. They all sort of do their own thing.
Anyway, grab a stripper squadmate and a pull-bot and start chaining powers to get warp bombs. You can do this from range and cover, but you aren't required to sit back as an Adept. Granted, it might be wise to get a damage protection upgrade or two before you charge everyone, and advanced weapon training from DCC doesn't hurt. But by mid-late game I think it is actually difficult for a couple of classes to keep up with an Adept and rounded out squad on a lot of missions.