How is that a good map? It's just a flat map.

It was a great CTF map featuring two indirect paths on foot and one larger, open path for driving on with hills that slightly impede movement if you drive off the trail.

The base featured a sniper rifle up top for zoning at range, a shotgun inside the base for close quarters defense or invading bases offensively, and a teleporter that would bring you halfway across the map.

In the center of the map you had a fuel rod gun that would provide strong, anti-vehicle support. The teleporter brings puts you on the far right side of the middle of the map, with each of the two bases teleporters landing you a fixed distance on opposite ends of the fuel rod gun. Cloaking fields just further on out on the edges of the map away from the fuel rod gun which were good if you were on foot and wanted to avoid vehicles mowing you down.

Capturing the flag usually entailed having a driver drop you off in a warthog, or using one of the indirect footpaths for a more stealthily approach. The base has three entrances: one in the front, one in the rear, and one directly on top that drops you onto the flag. This meant that the shotgun carrier couldn't just camp one of the entrances to deny you access to the flag.

Once you have the flag, returning on the direct path was faster on both foot and vehicle, but you were visually in the open and exposed to sniper fire, enemy vehicles, and the anti-vehicle fuel rod gun. The slower, indirect routes were only navigable on foot, but provided you cover that could keep you hidden and an overshield that would be useful once you re-entered the exposed parts of the footpaths.

tl;dr: Blood Gulch was not just a flat map, but rather a well-thought out map that required teams to coordinate to utilize and compete for resources on the map, and offered multiple routes that could be used and needed to be defended by your team.