That's not true. Cardano already works as a decentralized currency, and it also supports native third-party tokens and NFTs. Their smart contracts should go live in a few months. Cardano has one of the most detailed development roadmaps and their development has been maybe the most active of all blockchain projects. They have also released a lot of peer-reviewed research papers on blockchains, rather than relying on genius hackers. Cardano is based on a provably secure proof-of-stake protocol called Ouroboros. They also have Philip Wadler on their team developing their smart contract language.

https://docs.cardano.org/en/latest/explore-cardano/relevant-...

That said, I don't believe that there's an actual demand or need for smart contract platforms, or that it makes sense to build new currencies that are tied into these platforms.

Also, proof-of-stake is not very secure, and Cardano has admitted this by supporting Ergo, which is a new smart contract protocol based on proof-of-work. However, PoW needs a lot of hashing power to be secure, so Bitcoin with secondary smart contract layers such as Rootstock and RGB are actually the best option (if there's a need for them).