Some blockchain projects claim to be more decentralized than BTC.
Do they succeed in this regard or do they face similar challenges?
What lessons could BTC learn from these projects, if any?
What do you mean by "decentralization" Name one project that claim this and i guarantee that, those projects haven't got any real stress tests, or serious attacks in levels of bitcoin.
Yes, one could argue that huge mining farms could bring down decentralization and there could be ways to combat this, or that when majority of that mining is controlled by specific country, it's a bad thing. But when BTC doesn't have a company that regulators could attack to, it's isn't centralized around it either, unlike some altcoins, or even worse, altcoins with private source code.