But that is not a very large specific sequence of different types of amino acids.
Big fail there/
No. There was no fail at all. That was not the purpose of the experiment. The experiment was very successful.
Okay, it is obvious that you have no clue what you are talking about. The Miller Urey experiment was designed to see if amino acids could form naturally. That is all. At that time it was thought that they could only be made by existing life. We now know that to be wrong since there are several sources of amino acids. But if that was true, which it as not, then abiogenesis would have been impossible.
Some people over state the Miller Urey experiment. It is evidence for abiogenesis since it refuted an old wrong idea. But a theory is needs a lot more than just one solitary piece of evidence.
Let's use an analogy outside of evolution. Let's say that there is a murder trial. The defense tires to argue that the defendant was out of town and could not have committed the murder. The prosecution shows that he was in town. Now is that evidence for the prosecution? Yes. Does it prove beyond a reasonable doubt that the person is guilty? Not even close. It takes more than one tiny piece of evidence to convict someone.
What the Miller Urey experiment is is a test of deniers of science. If they deny that it is evidence then they are clearly being dishonest. Oh,, and if someone supporting abiogenesis tries to claim that it is "proof" it also shows that that person has no clue.
You really should learn what is and what is not evidence.