Large cryptocurrency networks like Bitcoin are extremely hard to execute a 51% attack upon due to their size. Though ultimately there's no perfect solution. As the saying goes, democracy is 2 wolves and 1 sheep deciding on what's for dinner.
But you can't use bitcoin or other blockchains with large cash flows as information storage at scale, since they use them to make transactions first and foremost and can't hold a lot of other data.
For many applications, it's possible to commit just a Merkle tree root hash to the blockchain and still get all the properties you care about, while only using O(1) blockchain storage.