The underlined part might have more to do with your DM then the actual system itself. Can you give us some examples of combat encounters you've faced?
If we're going strictly by anecdotes here then I gotta say I've experienced some of the same and some of the opposite.
I played a Warlock in the Keep on the Shadowfell module. I had fun playing the character, but I would have had more fun if not for the fact that KotS sucks and the DM was railroady. In this case, the combat encounters in general did tend to have very similar flows, but this could have been remedied by adding a greater variety of traps, hazards, and terrain features to the battles, and if the DM had integrated skill challenges into the game beyond what was pescribed in the module. I wanted to use bluff and intimidate to force enemies to retreat. The DM wouldn't allow this even though it's allowed in the rules. I wanted to knock enemies out, capture thim, and perform a skill challenge to interrogate them or even persuade to join the party as companion characters. There are guidelines in the rules. The DM didn't use them. It's his call as the DM of course, it's just really railroady.
I'm currently playing a half-orc tempest Fighter with a hook for a hand and a handlebar moustache in a PHB game. The campaign setting is based on the popular Castlevania games.
First off, my fighter played a lot differently from my Warlock in the previous game. Beyond the obvious ranged vs. melee divide that separates Warlocks and Fighters, my man 'Captain Conrad' was exceptionally good at charging and making multiple attacks each turn against two or more enemies at once whereas my Warlock 'Nevik' was geared more towards blasting enemies and healing himself. You might think it's all the same, but I saw a stark difference.
The DM in this game has done a very good job of making combat encounters exciting and dynamic.
The first battle against zombies and a warg was fairly standard, of course. It was a good introduction though.
The second battle required the party to help a small group of adventurers cross a street without being noticed while monsters roamed the city. We ended up fighting many fleanmen that bounced around the street like billiard balls, then we fought a homebrewed Frankenstein's Monster boss with an electrical attack. The terrain features here were quite interesting and there was lots of room to fight.
In our last battle we fought against and imp, and his skeletal guards, then several animated cherub statues that were guarding a crypt. The arena was a lot more cramped than any of the previous encounters, and the pillars and sarcophagi made for interesting terrain. My man Conrad found an apparently magical rosary that made him invisible against the statues. That was pretty fun.
I also DM games myself when I get the chance.
One dungeon I ran featured a battle with a giant centipede that popped out of a coffin and scuttled around, leading the party on a chase through all the chambers of the dungeon. The centipede made its last stand in the sludge pit room, where it dived into a sludge pit that was connected to another through a tunnel under the floor. The centipede would pop its head out of one pit, spit some goo out, then dive back in to reappear the following turn in the other pit. It was fun. The party included a brother/sister dragonborn duo. One was a dragonborn Cleric, the other was a dragonborn Rogue. They both played very differently.