Trust wallet is a non-custodial wallet and it gives you control over your assets, but it is a closed source wallet and that does not make it a good option to keep your assets. Someday there could be a bug or vulnerability in trust wallet that will cause you to lose your money if you use it, just as it happened with Atomic wallet, because people cannot verify its code; thus it is never a good thing to use a closed source wallet, and trust wallet is one.
You are right that Trust Wallet is not best choice for storing your money because it is closed source. This means that nobody can check code to make sure it is safe. If there is mistake or weakness in code you could lose your money like what happened with Atomic Wallet. On the other hand open source wallets are safer because many people can check the code and make sure it is secure. So it is usually best to use an open source wallet to keep your money safe.