Just had to wait for all the old British voters who supported it to age out.
I think if they'd just allowed a second vote once the terms of leaving were known, that might not have been necessary.
It's not quite a vote on the actual terms of the deal, though I'd argue that's a pretty high bar to set. Negotiations are hard-fought compromises, and subjecting that to yet another set of fingers in the pie makes practically any agreement impossible.
There's a reason we have representative democracies. And the representatives chosen were clearly sent to make Brexit happen.
The original referendum was much too vague, and should never have happened. And the 2019 election wasn't really a great measure of the support for Brexit; it's easily blamed on Corbyn's many failures (and he promptly resigned).
But I'd say that Remain had about as many bites at the apple as is reasonable in a democracy. A whole lot of bad choices were made, and there's plenty of blame to go around. The UK democratically made a bad choice. And I don't know of any good way to fix the fundamental problems with that.