My point is that they will use onchain transaction anyway.

Not necessarily. A scaling ceiling without a viable second layer will prevent a lot of usecases from coming to bitcoin. Or will force those usecases to use custodial bitcoin. 

rijndael

However, I find it funny that narrative "LN is dead" seems to be contradictory to "Bitcoin security is under threat" since if there is no robust 2nd layer, many transactions should settle onchain hence there will be some demand anyway.