> Why do people keep parroting this false trope?
Because it looks consistent, it's incredibly close to actual facts and it serves the narrative well.
But yeah, it is false.
First of all, broadly speaking, Budapest memorandum was not broken at a scale people think it was. The memorandum is quite short, go read it and decide for yourself whether it was failed. Bear in mind that the memorandum has no legal consequences, it's not binding at all.
Second, what you have said about the nukes is mostly correct. I have been living in Ukraine since before the independence and up until the war and let me tell you: people in the West have no idea how poor Ukraine was at the time. A wasteland. There was no funds to fuel ambulances in Kiev, let alone maintain the extremely expensive nukes. Nukes have an expiration date, and they would be rendered useless by the time Ukraine scrambled funds to maintain even a single one of them. Leave alone the fact that there was no (extremely expensive and complex) service facilities, no fissile material to maintain the nukes and no ways to procure or produce one.
Third, people in the west have no idea how corrupt Ukraine was (and I hate to say it - is). There is no doubt at all that some of the nukes would be lost.
So, there is no conceivable scenario in which Ukraine gets to keep and maintain those nukes in the nineties.
(I hate to say all of it as I am ukrainian.)