Telepresence works fine in the civilian world, where you don't have someone jamming your GPS and comm links. It fails dramatically when you're fighting someone with decent technology. Definitely not a "solved problem." Look at how the Iranians managed to capture an RQ-170...

If the US tries to fight a near-peer opponent like China or Russia, GPS will be jammed, satellites will be either blinded or destroyed, and both UHF and VHF comms will be either jammed or severely degraded. Just recently a US Army General was bitching about how advanced the Russians were with their ECM/ECCM in Ukraine. The Russians are extremely good at this.