They are both useful. Monero is a bit more tricky to use, there is no concept of Lightning network, you still have to wait around 7 minutes for the transaction to settle.
It's not bad, but it is different. The transparency in Bitcoin is a feature not a bug.
It very much is not. If I use cash to commit a crime but then deposit it into a KYC bank account which is then used as a side channel to get me caught does not mean its the cashes fault.
XMR privacy and anonymity can not protect you from going out of your way to convert it into inferior surveillance currency which then gets you busted.
That's basic logic and should be a obvious technical limitation.
That's more the fact that lightning is a bit of a pain to use. It has a chicken and egg network growth problem, which is doubled on top of the chicken and egg problem of its host crypto
That does not make any sense. btc even lightning still has about 100 times the user and ecosystem. Nobody uses it because it obviously it is not secure.