Fundamentally misunderstands the issue(s) involved.
Planetary destruction has been a thing for tens of thousands of years. Hell, anyone with a freighter is able to depopulate a planet if they want merely by crashing into it at relativistic speeds.
Three ISD's had the firepower to carry out a Base Delta Zero in a matter of hours while also preventing flight from the planet. One on their own could do it if they didn't care about fleeing residents.
Defending against these kinds of attacks generally takes having planetary shields, and those were both incredible expensive and uncommon installations.
What made the Death Star special (well its superlaser at least) was that it could blow up worlds even if they were protected by the strongest possible shield generators.
More realistically, the Death Star was a fully mobile fleet base, dry dock, construction facility, etc. Once it proved the ability to blow up a planet through its shields, all the DS needed to do was show up in orbit and order the planet to lower its shields so that the invasion can commence because the other option is that the DS just blows up the planet and gets on with life. Drop the shields and the DS launches the kind of invasion and suppression force that can take and hold even core worlds with trillions of residents.
The other issue with the video is underestimating the sheer expense involved in building and maintaining a Death Star. Even if you have the plans, the DS 1 cost a noticeable percentage of the Galactic Empires total budget, took more than a decade to build, and required all manner of infrastructure. The DS-2 was faster and better (most of the infrastructure already being in place) but it still cost a staggering amount of resources.
Building a DS from scratch, even a crude one, is something that only a handful of entities in the galaxy are really capable of. Even fewer would be able to pull it off in secret or with any kind of speed.
And then, you have a Death Star. Good luck fueling the thing.
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I mean the New Republic was a horrid government with a great many issues, but Death Star proliferation was never really a serious issue or game changer. It was just a fact of life that living in the SW galaxy, your planet might get blown to bits by a madman.