15 years
is early days when the technology is completely novel. For reference: the internet started in 1969. It took 30 years for it to see mass adoption.
Ethereum is extremely primitive at the moment. You reveal your address, and all of your transactions, to the entire world, when you use it. Scalability of L1 is limited to 30 transactions per second, while L2 is still in beta, with centralized coordinators.
With more development, people can conduct transactions while maintaining total privacy, and the public blockchain can, with the use of temporary data layers (EIP-4444 in Ethereum), sharding and Rollups, process 100,000 transactions per second while maintaining the decentralization, tamper-resistance and permissionless-ness characteristic of blockchains.