For a FPS, sliding around that can knock a person to the ground rendering them practically unable to respond is a bit idiotic! And the Grenades are a useless addition to the game, I can hardly tell when one has gone off? And don't get me started on the aim, I was excited about this game, but it shall be getting returned tomorrow morning!!
Unable to respond? Seldom do I ever die when Im knocked down, its pretty easy to spray and pray back at them, and if they are close enough to slide at you, then they are close enough for you to spray and secure a kill. Besides, they shouldnt be able to close enough to slide at you in the first place if you were doing it right. I really like this feature.
In terms of grenades, I like the fact that they aren't as OP as like CoD/Halo/KZ nades (Unless buffed). They add a more of a tactical element to 'spamming' nades. (Which is another great feature they have added, nade cooldowns prevent the spam is glorious.) To see if you hit an enemy with one, look out for the hit indicator, the red squarish outline you get when you deal damage, and grenades more often than not, if within hit range, knock the enemies down, so keep an eye out for a knockdown exp pop-up to know you secured a hit. But don't be expected to get many kills with them.
And if you had tried enough weapons you'd find that aiming isn't always that bad. Sure, some weapons have crappy stability or accuracy, but if you make the right weapon choices and customise your weapon to suit and increase the factors that hinder your aim.
But sounds to me like you would like a run 'n' gun shooter with the kills spoon fed to you. I normally wouldn't promote people to return the game, but I think this game isn't for the simple mind.