Using words like "somehow" doesn't help your case at all.
I think this word was used, because there is no BIP that you could follow step-by-step. But I know it is possible, you can try Homomorphic Encryption, and then come back with news like "Homomorphic Encryption cannot solve this, because of that". But I think you will also see, that it is possible.
so if you want to have something that is stored by every node forever then you have to store it in the utxo set
You never need to have anything that is stored always and forever, by every node. Putting data in OP_RETURN is better. Putting them as a witness is better. Not putting them on-chain and committing to them is better. There are many ways that are better (and cheaper) than trapping coins.
if that was the case then why wouldn't bitcoin be doing that right now?
Because programmers have more ideas, than they can turn into code in their lifetime. Also because people are unaware of the technical details behind some ideas. Some altcoiners could stay with Bitcoin, if they would know, how many things they could do, without creating any new coins. For example this one,
Using Merged Mining on a separate zero supply chain, instead of sidechains. You know what was
the first response? The first sentence was "I proposed something similar years ago". You know what does it mean? It means many people have many ideas, but they have more of them, than they are capable of turning into practical software. And there were many such cases, where someone proposed something, and received a response that "something similar was proposed before". Here is another example:
Adding SIGHASH to TXID. And
the first response. The first sentence was "Have you seen the inherited ID proposal from John Law on this list?". After reading more and more such examples, the conclusion is simple: people have many ideas. But having some idea and sharing that is one thing. Coding all of that is another thing, much harder, and that's why you don't have such features yet. But I think they will come, contributions are welcome, to make it real, it is needed to turn ideas into code.
because you seem to have a disdain for people you deem to not know as much about the topic as you do
I prefer talking with people that know the topic, instead of people that are polite. They don't have to use nice words. Especially when they are right, for example in case of this topic. It is derailed. It should be splitted somehow.
there may not even exist a public key that hashes to it
Of course. In case of hash functions, it is possible to have some hashes that are unreachable, and that no message can be hashed to that. But it is hard to prove it, without breaking such hash function.