So, just for a different perspective, Taiwan has a relatively simple tax filing experience, and the government invests significant resources to make as simple as possible (which does result in many people paying their taxes properly, on time). While their digital tools for filing taxes make the telegraph feel modern, the "in person" experience is full of helpful people and takes about 90 minutes including travel time…
That's America that's out of step. Almost all other countries only tax their residents, not their residents plus citizens. It's normal to tax worldwide income.
I told the British tax office that I'd left the country. They sent a refund and final statement a few months later, and we haven't communicated since.
If I had, for example, a house in Britain being rented out, I'd need to declare that income to my new country.