Starkiller Base is the worst part of the Sequel Trilogy.
And I don't just say that because it's the first obvious major problem and the thing that turned me off the Sequel Trilogy.
Compare the Death Star to Starkiller Base, the first we hear of the Death Star it's Darth Vader having just killed a bunch of people over plans to the thing, the first we hear of Starkiller Base it's Han with a plan to infiltrate the place. Half of Episode IV is just dealing with the PLANS for the thing and when we finally blow it up it's the climax of the whole thing and the culmination of a bunch of people's work that we actually SEE.
The Death Star's fatal weakness is a single shaft, a near impossible shot, a critical weakness mandated by the reactor design and mitigated as best as possible. Starkiller Base's fatal weakness is, in no particular order, a centralized generator that has no reason to be centralized, insufficient sensor coverage, no Interdictor Fields, and apparently being waaaaay too obvious(how does Han find it? No idea).
Starkiller Base is a pile of idiot balls that is introduced clumsily, handled entirely in the background, has no impact on our heroes, and completely fails to be a stand in for the Death Star.
No seriously, compare the one shot the Death Star got off vs the one shot Starkiller Base got off, the Death Star blows up a main character's home planet in front of them, massive emotional damage to a main character so we have a reason to care about destruction too large for humans to really grasp, Starkiller Base blows up a bunch of planets, I have no idea which, none of the main characters give a shit about any of them, it's pure spectacle and has less emotional impact than a fireworks display.
Compare the death of the Death Star to the death of Starkiller Base, one get's blown up after a hard fought battle to get the one guy who has a chance to make the shot into precisely the position to do so, every supporting character has put in on screen effort to get to this point, and Luke's Force Assisted Perfect Shot hits the audience in the feels as surely as it hit the Death Star. Starkiller Base get's blown up because characters have been planting satchel charges in the background of dealing with Kylo.(and btw, how fucking pathetic is Kylo that characters have the spare attention to do anything but not die, he is so blatantly "Shitty Vader Knock Off" it's not even funny, which just makes Luke's reaction to his "spark of darkness" all the more ridiculous)
The Death Star gets off its one shot while it's still invulnerable, while the audience is still unsure if it'll actually be destroyed, it's a demonstration of power absolute. Starkiller Base gets off its one shot after it's already been infiltrated and a bunch of the fatal satchel charges have been planted, it's the last gasp of a failed power play.(that the First Order still somehow takes over the Galaxy really begs the question of why they ever made it)
The destruction of the Death Star is a major turning point in the war, and it's treated like it by the story, Starkiller Base is a footnote and its treated like it by the story. But both are also absolutely central to their movie.
The Death Star is a character, Starkiller Base is scenery.
EDIT: just in case anyone is wondering why I'm back to ranting about the Sequel Trilogy, I was just in the Dentist for temp crowns so I blame local anesthetic)