It's literally unchanged from EU/EW/LW. Exposed shots just means you take your full aim into account on that soldier. Plus or minus aim bonuses. All you get is a crit bonus. Even at the start your soldiers have 65 aim. That's marginally better than a coin flip, but when you factor in low and high cover (+20 def / +40 def) it's a drastic hit to your aim that of course if you just grenade the cover away you already have 50-100% better chance of hitting your target than they were in cover if you didn't already kill the ADVENT trooper behind it or bring a sectoid down 1/4 of it's health and force it to run into cover again.
It's no surprise either Grenadiers are stupid good when running down pretty much either end of the perk tree they have a bunch of cover destruction and guaranteed damage and party debuffs. Anyone who even watched Beagle slowly take apart Long War (as much as most people can, it's still imbalanced, even against him and it gets the better of Beagle sometimes - we're talking about someone who refuses to skip missions in Long War short of a literal roster disaster or because the endgame is in sight) or played Long War knows to conquer some of the other threats like 60+ hp sectopod bosses or a pod of 6 or so 30hp chryssalids and a 75hp boss chryssalid in a turn or two, you need to employ things like party debuffs and optimising your turn to a ridiculous degree and having as many buffs for you/debuffs against the enemy to the fight in your favour to basically kill things as fast as you can.
Honestly I'm not surprised and anyone who's put in even a decent amount of Long War play even on normal difficulty will probably know also how to maximize the gains on their turns instead of doing suboptimal things like plinking at targets in cover for 1/4 chance to hit, etc.