DeFi, in a reduced form. Decentralized exchanges (Uniswap, Curve) and lending protocols (Aave, Compound) are still running. Total value locked in DeFi stabilized around $50-80 billion, far from the $180B peak but also far from zero. Stablecoins (USDT, USDC) became genuinely useful for cross-border payments, particularly in countries with unstable currencies. This is probably the most real, lasting use case to come out of the entire Web3 era.
Blockchain infrastructure. Layer 2 solutions (Arbitrum, Optimism, Base) solved a lot of Ethereum's scaling problems. Transaction costs dropped from $50+ during the 2021 mania to fractions of a cent. The technology got better, even as the hype disappeared.
Zero-knowledge proofs. The privacy and verification technology that emerged from blockchain R&D has applications well beyond crypto: identity verification, supply chain provenance, and secure computation. This may end up being the most valuable technical export of the Web3 era.
Tokenized real-world assets. Banks and financial institutions quietly started tokenizing bonds, treasury bills, and real estate on blockchain rails. BlackRock launched a tokenized money market fund. This isn't the "democratize finance" revolution Web3 promised, but it's real institutional adoption, just not in the way anyone expected.