Cosmos solves three primary problems in blockchain: sovereignty, scalability, and sustainability.
Sovereignty: Blockchains today encourage all economic activity to take place on a single chain. This mindset leads to centralization in governance, ongoing costs for smart contract developers who build on these chains, and high fees for users of congested chains. In contrast, the Cosmos SDK is free for developers and allows them to build sovereign blockchain apps without ongoing costs.
Scalability: No matter how many transactions per second a blockchain can claim, in Cosmos, developers can always improve throughput with horizontal scalability. Scalability can be achieved by (1) duplicating a blockchain to relieve congestion or (2) splitting up the apps on a blockchain into multiple application-specific blockchains. Interchain token transfers allow these multiple chains to continue as one network.
Sustainability: Cosmos blockchains use an efficient Proof-of-Stake (PoS) consensus algorithm for securing the network. This PoS algorithm reduces the Cosmos carbon footprint by more than 99% compared to Proof-of-Work blockchains like Bitcoin that has a carbon footprint roughly the size of Switzerland.