Yeah, she's definitely in the git gud selection of heroes (alongside Genji, Widowmaker, &c.) where someone who doesn't know what they're doing is going to suck. If you're new to the game/role/genre, probably not a good pick. Zarya needs good timing and judicious use of abilities, almost every aspect of her kit depends on it.
Basically the way I see it is that anyone who says she's too squishy is being aggressive in an inappropriate way (constant slow frontline pushing rather than bursts of fast pushing); anyone who says she doesn't do damage doesn't know how to use her bubbles. You can maintain ~60-70 energy pretty easily even against good teams, especially if you're working in tandem with someone who wants to go up into their faces and trade damage, and if you're at high energy you're melting motherfuckers.
Also, uh, as for her M2 damage compared to Junkrat, Zarya's base grenade damage with no amplification is 45 with a 2m AoE. Junkrat's grenade damage is 120 with a 2m AoE. Yes, it's a third of the damage. If you're still keeping track, that means that a tank's spammable low-damage secondary fire soft CC tool does a third of the damage of one of the most consistent damage farmers in the game; it does better damage than McCree's bodyshots beyond ~30m. Now obviously with charge that increases (to a maximum of 90 damage at 100 energy), but if you're not pushed into beam range and melting people by then you're doing it wrong (since a 100 energy beam does 190 DPS)