There are multiple onuses, determining whether a status quo should
change is only one of them. But where status quo is also an expression of power, there can also be an onus to justify its existence. If that scenario arises, generally those demanding change have already met the criteria (at least those available to them). At which point the status quo thing is in the same philosophical position of making a claim and has the logical burden of proof that the status quo itself is justified.
This reasoning is sometimes used hastily in radical-left politics, eg in some forms of anarchism where any power relationship is subject to justifying its existence. But, and I’m saying this no longer an anarchist, you don’t need to be a radical or revolutionary to see it play out.
This is essentially exactly how many cannabis legalization efforts have worked. After decades of dedicated effort to establish plurality support for questioning the status quo of prohibition, the question of whether prohibition is justified becomes scrutinized at a policy level and it the justification isn’t there. The only remaining barriers are weak pluralities and successful counter-marketing. If either of those are absent, the unjustified status quo has been changed.
Which is all to say, the onus isn’t on anyone to unjustify something that’s wrong, the onus is to motivate people to know and care that it’s wrong, and to agree that it matters. From there, the onus is the same as GP said: you’re making the claim, you defend it. Otherwise the assumption is just, like, your opinion man.