It can't scale up to handle the volume of transactions required for global adoption.
Bitcoin is the only decentralized, peer-to-peer system we currently have and it needs to scale to handle more transactions per second. For some reason this issue is being ignored by the developers and community when it should be main focus. The changes that have been made to Core recently would indicate that the developers and community want it to be slower and more expensive.
LN solved the problem to a certain extent but the reach of LN is still low and it's a sidechain.
Lightning is fast but NOT peer-to-peer or decentralized. This introduction of multiple intermediaries in every transaction will cause additional fees and transaction monitoring. Unfortunately channel liquidity provides an issue for merchants as well. They must provide inbound liquidity or pay a recurring fee for a 3rd party to provide it who can monitory their transactions.
The main point here is that over time the channel providers will consolidate and become the future banks.
Bitcoin is a bad payment method if we compare to the traditional payment methods we have available in the market.
Bitcoin has solved several problems traditional payment methods have not. It is decentralized, peer-to-peer and has a limited supply to name a few. The only thing we need to fix is the speed of transactions. Lets focus on that. The solution shouldn't make it slower and more expensive. Don't centralize it. Don't add 3rd party intermediaries, and don't increase the supply limit of 21,000,000.