There are chains focused on powering omnichain applications, yes. Still very early, but there are teams working on solutions.
I do agree that the fragmentation inside DeFi is insane. Impossible to achieve liquidity efficiency on the scale of centralized platforms -- crypto or tradfi.
One thing I've been thinking about is consumer aggregation apps. We have the likes of 1inch to aggregate DEX liquidity for a specific chain, but not a lot of cross-chain aggregation. A protocol that can split your perp trade between dydx, vertex, and gmx would be pretty cool and enable joined liquidity for the user.
That said, again, Uniswap is basically a different and siloed protocol on each chain. And we need solutions that help DeFi primitives be truly multi-chain and share liquidity across deployments. A money market that can route lender funds from one chain to another based on where demand to borrow for an asset is will undoubtedly be closer to equilibrium (in rates) than any siloed money market. I think the main thing holding us back here is the state of bridges and vulnerabilities stemming from the complexity of the smart contract suite.