I wasn't a big hardcore fan on BF3, but right now I despise it in BF4 because:
a) As JR said, it sucks ass if you're new and don't know the maps. You don't know the usual hiding spots yet, you get smashed on by random snipers. Oh, hey, I instantly died from a random sniper bullet on a huge Conquest map, here's to never ever finding out where he is so I can get revenge.
b) I'm a big fan of popping in and out of 3rd person view in vehicles. It helps track the enemy jet you're chasing down, it's nice to see kamikaze C4 ****s trying to blow up your tank, and it's fun to watch you and a friend cruise around on a buggy and hit wicked jumps
c) Dorito's. Once again, the whole not knowing the map thing comes into play, but I'm addicted to spotting enemy combatants so that I or a teammate can chase them down and end them.
d) Motion sensing. I was flabbergasted when I threw a motion sensor ball in hardcore and it did absolutely nothing. Why is it even an option in HC?
e) Ammo. I don't know how much ammo is in my magazine, I just got the game, give me a break.
f) Spawning. You can only spawn on one guy in your squad? Oh, and he's hanging out at the back of your base taking 2000 yard potshots at tanks with sniper rifle? Gig 'em.
g) Your own mines take out your ally's vehicles. Seriously? Ok, yeah, it's "realistic." Too bad you can literally knife through a chainlink fence in one swipe. Just like in real life.
For me, I play the game to have fun, not to replicate a real-life ground battle that will never ever come close to a real-life gun battle. I know that's not why everyone plays HC, but I really don't know why some people are so dead-set on it...maybe so they can talk down to "softcore n00bs." Anyway, if you're complaining that it takes to long to kill an enemy, then just shoot them more.
Sidenote: You honestly can't just jump in a friend's party? Really? WTF Bill Gates?!