It just presented one dull 'steel cage death match' fight in tight quarters after another.
Ironically, they
should have paid more attention to MMOs to counter this exact problem. MMO designers have long been aware that pointless and drawn-out trash fights are a problem. You need to either be building up to something through them, or you need most fights to have something interesting in or around them to keep people engaged. Two key examples come to mind, one from World of Warcraft, the other from FFXIV.
In WoW, a dungeon I really quite liked was Vortex Pinnacle. The story part isn't as relevant here as what they did with the fights between bosses. Several of the so-called "trash" fights are actually
pre-teaching you how to fight the final boss. There are flattened tetrahedral pyramids of lightning that will have monsters in them at various points along the way; you need to drag these guys out, and (ideally) position any ranged DPS inside them, because they reflect away ranged attacks. Useful stuff, if you can take advantage of it. But it becomes
clever when it gets to the final boss, who has a room-wide and nominally unavoidable party-wipe attack. Except...to charge it up, he has to create one of those squashed pyramids of lightning, which deflect away attacks. This means they can avoid the usual blatant telegraphing present in most boss fights, because they can reasonably assume
you already know how this works, having literally just taught you. That's one way to make "boring" fights work--give them an interesting mechanic the players can learn from, so that when they get to the big boss, they can leverage that knowledge.
By comparison, in FFXIV, there's a pretty neat dungeon (not my favorite, but a neat one nonetheless) called the Drowned City of Skalla. The designers kept things fresh by featuring a wide variety of different creature types as you push through it. The opening few fights are all ocean-related creatures, due to being deep underground and only accessible through a briny loch, with some creatures being big heavy-hitters, and others being numerous ankle-biters. Then, in the following area, it's all earth-y stuff, sand creatures and earth elementals, and they do lots of big ground AoEs that hurt if they hit you, so you need to stay nimble. Then, in the lead up to the final boss, you get a number of unusual mechanics like targeted cones, or unusual movement modes between fights (turning into...honestly they look like floating trash bags!) No two packs are ever
quite the same, and you really feel a sense of changing theme as you move. This leverages theme and mechanics to try to have even the "boring" creatures incite aesthetic and tactical pleasure in the fighting.
It's just such a shame that so few of the designers at WotC actually understood how to make 4e's engine sing. It's, frankly, like they were trying to design fights that specifically presumed 3.x elements like the full attack (which discourages any movement unless absolutely necessary) or the inability to do support things
and combat-advancing things in a single turn (due to action economy), while avoiding many of the things that make 4e rich and interesting (terrain challenges, minions with creative tricks, solos/elites that undergo a radical shift when bloodied, etc.)