Mainly because it promotes third party custody so it allows Bitcoin inflation, like how "paper gold" (just papers pretending to have amounts of gold in vaults) can allow manipulation of the gold price Also because it has issues like transaction failures that Bitcoin doesn't have, and it just makes Bitcoin more confusing and scammy-looking to normies

Fair enough. I have a different perspective on it. While I run my own lightning node, I also use some custody lightning and liquid services. Also, I think the vast majority of people don't actually want to self custody, even if I wish they did.