Monero cannot scale the same way as lightning, and consumes substantially more space than Bitcoin transactions.
Discussion
Monero is on chain, right. It has a block time of 2 min which is very good. But ag least your payment goes through, Lightning has no guarantee for that. The fees for Monero are super cheap, with LN you can have some super bad experience. You cannloose money with Lightning etc etc. So the tradr offs for Monero are much less. And LN will go down as soon as the whole infra will need licences and that will come.
lol
Monero is bringing scalable L2s with FCMP, so first part will soon be moot. Encrypted blockchain + L2s are probably the best privacy you can get.