Another issue I have with 5E's combat system is the way there's an 'out' every round for abilities and effects. I get that it's an effort to keep players 'in the game', but again, it tends towards this mediocrity where it's hard for anything interesting or truly dangerous to happen.
Case in point: : Last night in our 2E game, the DM presented us with a pair of ghasts that a bad guy let out of cages to come after us. The DM role played the thing so well that initially we didn't even realize the monsters were ghasts, or even undead. A couple rounds into the fight, my superstar 13 WIS cleric (13 being his highest ability score!) got paralyzed and knocked down to 'desperation' HP with auto hits. There was no save at the end of the round- I was paralyzed for more rounds than the fight was going to last, out of action and now a liability to the party if they wanted to try and save me. One ghast was hauling my paralyzed ass away for a live feeding. 50% of the party was down and paralyzed before we eked out a victory. I didn't participate or say a word (except to laugh at my own predicament) the last 4 rounds of the fight. I was actually thinking about what my next character was going to be and wondering if this was going to be a TPK. And make no mistake- just because my character was out of action and I wasn't rolling dice didn't mean that I wasn't having fun or being hugely entertained- I was!
In 5E, you won't have fights like that because you get a save every round to end the effect. It goes back to what another poster was saying about the monsters in 5E just being HP bags with abilities tacked on- and most of these abilities are nerfed. A vampire's drain effect is an HP thing and goes away after a long rest? Well, vampires are no longer a threat to be feared- I'm looking at you, Strahd! Losing two levels permanently (Restoration / Wishes notwithstanding) made earlier versions of this creature something to be feared, respected, perhaps even avoided until you, too, were truly powerful. A couple hits from an old school vamp and you were either dead or so reduced in levels that the entire adventure just became certain doom. Same thing with petrification effects from a basilisk and so forth. In older editions, a basilisk could turn you straight to stone on a failed save and you were dead until the survivors went way out of their way to find a method of bringing you back. In 5E, you get two CON saves on successive turns against a DC12. I don't care who you are, those are nerfed abilities, and although I know not everyone sees it the same way, I feel they detract from the spiciness of DND combat.