Star Trek: Discovery crippled the Starship Enterprise in a hilarious fix for a plot hole that's been troubling fans since the series began. The Enterprise has always had a habit of missing the latest Federation wars, largely because she's frequently sent on five-year exploratory missions into the depths of space. When Discovery crossed paths with the Enterprise, she was returning from one of those voyages, but suffering from catastrophic systems failures.
These systems failures are the reason Captain Pike was forced to commandeer the Discovery to investigate the mysterious seven signals and the Red Angel. For the last few episodes, Starfleet has been desperately attempting to repair the Enterprise. The latest episode, "An Obol for Charon," finally revealed the reason why the starship has been undergoing these technical problems.
The episode begins with Pike receiving an update on the Enterprise's repairs. Federation engineers have finally worked out the cause of the Enterprise's critical system errors: the holographic communication system. Something about the holo-comms clashed with the rest of the Enterprise's systems, and caused them to crash. Pike orders them stripped out, undoubtedly more than a little relieved because he's never been a fan of them anyway.
This is actually a great fix for what had previously been seen as a major continuity problem. Star Trek: Discovery is set a decade before the events of Star Trek: The Original Series, and yet some aspects of the show's technology - such as the holographic comms systems - had seemed strangely advanced. Some aspects of this could be explained away because the Discovery is a science vessel, with experimental tech that may prove problematic and be discontinued. But the holographic communication system was prevalent across Starfleet right from the pilot episode, so it just seemed odd.
It's now clear why Starfleet abandoned this technology - it took down the Enterprise, their flagship. What's more, it's reasonable to assume the Enterprise won't be the only ship of the line to suffer these problems, so a chunk of Starfleet's best vessels will probably have been in trouble as well. By the time Kirk becomes captain, the holograms had been completely stripped out of every Federation system, which is why the starships all have the traditional viewscreens.
Of course, by the time of Star Trek: The Next Generation, Starfleet had found other uses for their holograms: the Holodeck. But Holodeck malfunctions were almost an everyday occurrence in that series, suggesting that even then it wasn't perfect. Fortunately, Starfleet had the sense not to hook critical systems up to the Holodeck, meaning the malfunctions didn't take the Enterprise down.
Star Trek: Discovery streams Thursdays at 8:30pm on CBS All-Access and the next day internationally on Netflix.