If some new tech comes along and makes decentralized, trustless timestamps not only possible but also safe, secure, cheap, and fast, then I'm certain someone will launch an altcoin based on that, and it might even do well. But we are nowhere near that yet.
This is genuinely an interesting question in how you would do that.
If you had perfect trustless timestamping, you could have a new independent banking method. But I can't conceive of how it would work without the timestamp eventually being tampered with. With any currently conceivable method, a trustless, decentralized timestamp is impossible.
Besides tampering with code, you could modify the time stamp through any number of methods:
add an extra network routing node between the miner and network to cause a latency delay
add extra physical wire between the clock and computing hardware, causing a the node to appear nanoseconds later in time, which could cause collisions
put one of the nodes in orbit, making other nodes appear to sign after the space node which could appear to be a femto-nanoseconds earlier in time due rapid orbiting
Delays in either direction for a network that relies solely on timestamping would eventually result in collisions and insolvable headaches.
You would need a new physics method, like quantum entangled communication that instantaneously communicated with nodes and wasn't hampered by distances in communicating messages, or time dilation from the speed of light for when nodes are put into space/orbit. Current relativity physics says this is impossible to get around. Making a node appear moments in the future or past doesn't matter much for your currencies that don't matter much, but it puts a limit on the ultimate value of your network. Once the value becomes great enough, then someone will break it. No store of value is immune to that process of attempts at being broken as the currency grows in value, but the difference is that bitcoin has withheld its own whereas things like Solana regularly go down. There's no need to introduce more potential flaws to a network especially one that you want to hold immense value.