Just my two cents on map size being he key: One of the mods most played maps was RO_Berlin. I was basically on long corridor down multiple streets, around some corners leading to a bridge that needed to be taken. Infantry could take cover in the ruins on both sides of the street. Allies got a tank that would support the advance. Round time was one hour. The map was ugly compared to some other maps, but it was one of the most played maps because of the intensity of the firefights. Advancing even a couple of meters down the road was a tough and gruesome battle. Flanking obviously wasn't an option except for a couple of spots.
Then you have maps like TE-MyshkovaRiver, which is pretty open and has plenty of cap points, where it is basically impossible to put up a meaningful defense. Germans can just rush up to the next cap point and start to cap it 10 seconds after the last one has fallen. That is IMHO bad map design.
I think the most important aspect of a good map design (for RO) is to channel the firefights and discourage run'n'gun and encourage cohesion. I think maps, where a couple of players "flank" way off from the objectives (usually running around and fighting the couple of enemies that do the same pointless thing) aren't well made.
There are some custom maps, where the mappers just want to do too much, play mostly bad. They put up too many houses, and too many things. There's a forest, a base, a beach, a river, and so on, all on the same map. And often, there are also too many parallel objectives and options. This often leads to a mess off a firefight and undefendable positions.