I feel like a major limitation to a Stargate empire would be Stargate throughout.
A large enough military would need to be supplied at each Stargate to secure access. At a certain point, it is going to be difficult for the home world to supply all garrisons, even if some garrisons some self-sufficiency. Worse, if a garrison is self sufficient, how do you maintain loyalty to the home world.
Flash and Silverlight follow what I said. They were ubiquitous until the costs, being a bloated platform that couldn't be ported to smartphones, caused the industry to shift to an open model.
And messaging is a very old use of the Internet. IRC was created in 1988; Discord shouldn't be a thing based on what you've said.