Can you give us a few examples of combats that have been boring or un-fun? It's hard to diagnose "dull and takes forever" without a bit more detail.

Interpret "environmental hazards" a bit more broadly as "interesting terrain". An example from a set of combat encounters I ran recently, was a two-wave encounter with a bunch of lizardfolk.

• Combat #1: players are traveling through the desert, walking north up a dry riverbed with 8-10' high stone ledges on either side. A squadron of lizardfolk attack from one of the ledges: a few archers and a spellcaster rain down hell from their vantage point, while a few "cavalry" mounted on giant coyotes leap down with their mounts and engage the PCs in melee. The party is at a significant disadvantage because of being boxed in on the low ground, and the fight feels desperate and challenging.

• Combat #2: the party continues north, now wisely traveling atop the stone ledges rather than in the riverbed, where a number of the lizardfolk cavalry sped off to after completely ignoring the party. They come across a caravan being attacked by the other lizardfolk. However, the lizardfolk are down on a flat plane below the ledges, and haven't noticed the PCs yet. The party quickly puts together an excellent plan to ambush the lizardfolk, leap down on them from above, herd them into a Spike Growth trap, and save the civilians, which works out splendidly. The PCs feel powerful and heroic, all due to terrain and a bit of surprise.