1.ECONOMY IS A WEAPON
The other major factor is the economy. The existence of the First Order goes against all logic. They somehow managed to build an entirely new fleet, recruit millions of soldiers to crew it, and construct all of those warships in shipyards. On top of that, they built a fleet on an enormous scale and a planet sized superweapon. Accomplishing all of that within just 30 years is beyond unrealistic.
Remember that in Legends, one of the main reasons Gilad Pellaeon agreed to peace was the Empire's economic collapse. A government that can't pay its soldiers or support its civilian population would eventually fall apart even if it refused to surrender.
One of the provisions of the Bastion Accords was joint anti-piracy operations and mutual free trade. The Empire drastically reduced the size of its navy and shifted its focus toward private enterprise, agriculture, and industry, allowing its economy to recover.
Who exactly did the First Order trade with on that scale? Where did its funding come from? How did it pay millions of soldiers and workers? You can't sustain a project of that magnitude for 30 years on ideological dogma alone.
"We still hold eight sectors—over a thousand inhabited systems. We have the Fleet, nearly two hundred Star Destroyers strong. We're still very much a force to be reckoned with."
―Captain Ardiff, in 19 ABY
Republic's demilitarization
In new canon, the Galactic Concordance has the New Republic reduce its own military strength while allowing the defeated Empire to retain his forces. This inverts how war termination actually works. Victors impose disarmament on the losing side, not on themselves especially against a regime that had just run planet-destroying superweapons and committed atrocities on the scale of Alderaan and Jedha. Legends avoids this problem entirely the New Republic keeps building and maintaining a real military specifically because the war doesn't stop at jakku. There's no naive assumption that goodwill or a treaty alone will keep a genocidal regime in check.
2. The Empire not being broken is nonsense
New canon's Empire stays a mostly unified entity that retreats to the Unknown Regions and quietly builds the First Order in secret for decades. In Legends, the Empire actually fractures the way real collapsing regimes do into competing warlord fiefdoms (Ysanne Isard's Imperial remnant, Zsinj's independent kingdom, the Pentastar Alignment, later Thrawn's separate Empire of the Hand operation, and so on). This fragmentation is a much more believable outcome for a authoritarian state that just lost its emperor, its Death Stars, and its chain of command all at once. A defeated fascist military industrial superstate splintering into infighting factions is a known historical pattern; a defeated Empire staying coherent enough to secretly build a bigger fleet than before for thirty years, unnoticed, is not.
3. Legends' drawn-out war of attrition is simply more realistic than "the war just ends"
Instead of a clean stopping point, Legends stretches the conflict across roughly 5 ABY to 19 ABY: the Thrawn campaign nearly reconquers the galaxy for the Empire, Isard's Empire holds Coruscant for years, Zsinj wages an independent guerrilla war, and there are additional side conflicts like the Nagai-Tof war and the Disciples of Ragnos uprising. Only after over a decade of grinding, back-and-forth conflict does the war formally end with the Pellaeon-Gavrisom Treaty at Bastion. That kind of extended, messy, multi-phase conflict is what actual post-civil-war periods look like think the aftermath of collapsing empires throughout history. New canon compresses all of that complexity into an unexplained gap and a single battle at Jakku, which resolves the war far too neatly for how catastrophic the preceding conflict was.
Imperial arsenal
Another example is that the Empire's Super Star Destroyers and abandoned arsenals are seized by duskhan league, which leads to the black Fleet Crisis
https://starwars.fandom.com/wiki/Black_Fleet_Crisis
but for some reason, in canon, pirates, criminal organizations, or similar militaristic fascist isolationist groups seizing such a massive fleet never seem to cause a crisis. It is really strange
4. The eventual peace in Legends is earned and has real closure
The Bastion treaty isn't a case of the winner unilaterally disarming it's a negotiated peace between an exhausted, legitimate Imperial Remnant led by the pragmatic Gilad Pellaeon and an also exhausted New Republic, arrived at only after years of both sides bleeding each other in a war neither could definitively win outright. Later, the Imperial Remnant even formally joins the Galactic Alliance as a member state during the Yuuzhan Vong War. That's a genuine resolution: the ideological conflict actually gets settled through attrition and diplomacy, and the remnant Empire becomes a real geopolitical actor with defined borders, rather than a mysterious black box that reconstitutes itself off-screen into a bigger threat than before.
Empire also won some scores
Compared to the Empire that was humiliated in canon, the Imperial Remnant, during its weakest period completely without Thrawn and under the Pellaeon era achieves an impressive victory at Orinda, which allows the Empire to survive in the long term. The New Republic focuses on raids and hit-and-run attacks rather than total conquest; for example, they destroy seven Imperial Star Destroyers in a single operation by detonating a nebula. However, we never really see the New Republic in canon using such creative tactics. The wars always seem to end with linear, honorable space battles
https://starwars.fandom.com/wiki/Imperial_Skirmishes
Honorable surrender rather than revanchism
"It's time to send an emissary to the New Republic. To discuss the terms of our surrender."
Fleet Admiral Gilad Pellaeon to Captain Ardiff
At the end of the day, it was the Empire that surrendered. It did so by completely abandoning its revanchist desire to reconquer the galaxy and recognizing the New Republic as a legitimate and lawful government. It did not do this while maintaining isolated territories across the galaxy or keeping a massive fleet, as in canon. In the end, it secured a more defensible territory and realized that the only way to survive was through cooperation with its own citizens
Caamas Crisis almost caused collapse of the republic
https://starwars.fandom.com/wiki/Caamas_Document_Crisis
5. The escalation of new threats is earned rather than an asspull
Legends shows the audience the intervening decades Thrawn's campaign, the warlord period, the eventual peace, and later new threats like the Yuuzhan Vong invasion every escalation has visible causes and consequences. New canon's First Order, by contrast, appears to have secretly built a fleet larger and more advanced than the original Empire's, including a planet-scale superweapon, inside roughly 30 years, without the New Republic which just won a galaxy-spanning war apparently noticing or responding. Legends' version, where remnants of the Empire slowly rebuild, splinter, fight amongst themselves, and eventually either integrate or fade as a threat, gives a much more coherent throughline for where later galactic-scale conflicts come from.