Legit criticisms of Monero in comparison to Bitcoin: uncapped total supply, potentially undetectable inflation bugs, smaller community, smaller liquidity, more difficult to acquire, easier to attack, large tx sizes so the chain grows far quicker and potentially harder to run nodes (there are also counter arguments for all of these)

vs Lightning: Not instant, not as cheap, it's blockchain is a public global ledger that is forever (FCMP upgrade will change this)

vs other privacy tech: Although ring signatures have worked well enough so far, they aren't good enough for edge cases and in the longrun (FCMP upgrade will change this)