Of course, everything is. Doubling the speed of light means your network packets get there twice as fast, but accelerating matter to relativistic speeds, which too is limited by the speed of light, has less marginal utility from the doubling when it comes to energy needed for acceleration/deceleration and time dilation.
You're thinking of latency vs bandwidth/throughput. You might not improve on the latency part (speed of light), but you can increase the bandwidth (amount of data transferred per unit of time) just like a highway with more lanes can carry more people without increasing the individual speed of cars. You might even decrease car speed and still get an improved throughput overall.
Maybe quantum entanglement, where the original "portals" would be set up around the universe at the speed of light, but then data could henceforth be transferred between the portals at the speed of entanglement.
