Lightning adds a layer of complexity and additional failure points. It also centralizes power in the bitcoin network even further.

It doesn’t actually change anything about the fact that Bitcoin isn’t a currency: Despite the fact that it’s claimed to be theoretically able to handle millions of transactions per second, it only handles a few million per month or about half of all Bitcoin transactions after having been around for six years (and most transactions aren’t payments for goods or services). The vast majority of online commerce does not accept bitcoin nor any other cryptocurrency, which isn’t surprising, given that their values fluctuate wildly. Currencies need, acceptance and stability, neither of which applies to anything crypto.