The obstacles to indie RTS games aren't art style/production related. If anything, the top-down or isometric-ish view makes that part relatively straightforward.
The requirement for online multiplayer (while dealing with hundreds of units) is the bigger obstacle. Especially if they're working with Unity. Pathfinding (in a way that lets large swarms of units move smoothly through narrow choke points) is a non-trivial problem, too.
Then there's the design problems. How to get away from standard build orders, and how to make a game that's more accessible than Starcraft but still allows high-level competitive play.
The requirement for online multiplayer (while dealing with hundreds of units) is the bigger obstacle. Especially if they're working with Unity. Pathfinding (in a way that lets large swarms of units move smoothly through narrow choke points) is a non-trivial problem, too.
Then there's the design problems. How to get away from standard build orders, and how to make a game that's more accessible than Starcraft but still allows high-level competitive play.