Bitcoin has a scaling problem. It was designed to facilitate payments not dependent on trusted third parties, and in order to accomplish this the system needs to be verifiable for all users to ensure payments are valid without trusting the word of a third party. These two things are diametrically opposed.

Scaling has to go throught: Trustlessness Settlement Finality Cost Liveness Requirements Putting It All Together

To scale Bitcoin is more than just increasing the number of transactions it can process per second. We can do that right now with custodians. To scale Bitcoin is to increase the number of transactions that can occur trustlessly, with censorship resistant finality, without burdensome requirements of liveness placed on the user, and for a cost that a larger set of users can afford. If we can’t scale those properties, then Bitcoin hasn’t actually scaled, no matter how many transactions a second are occurring with bitcoin the asset.