LN steals transaction fees from BTC for it's offchain network
Transaction fees can go trough the roof so it isn't a problem as many on this forum will reassure you.
The problem is LN dependence on timelocks that will wreak havoc on the world if level 1 gets disabled for an extended period of time.
bitcoin is not ethereum to have its entire network crash entirely just because there was a fee rise. the higher fees don't "disable" the bitcoin blockchain, it will just cost more to have your transaction mined faster.