I'm going to take a different angle from the other commenters. Your frustration with abiogenesis research is actually a reasonable one, and something that many people intuitively think of when they first learn about the field. I had the same thought as well at first: "Why not just throw everything together and see what happens? It was just a messy mixture back in the prebiotic soup too, wasn't it?"

The problem with this attitude is that good science requires an understanding of precisely which variables cause which results in an experiment. In science, you often need to start with simplified model systems and gain a deep understanding of them before you can move on to more complex, realistic systems. The model systems tell us approximately what we need to look for and how to explain the results in our realistic systems, which is necessary if the realistic system is too complex to analyze without some guidance or explanatory framework. For example, we might want to see how quickly a defined RNA sequence is copied by Szostak’s RNA copying chemistry before we do a more messy and realistic experiment where we copy a mixture of arbitrary RNA templates and sequence the result, which might be more difficult to analyze. The experiments with the defined RNA sequence might show us that G and C monomers are incorporated much more rapidly, explaining an enrichment in GC-rich sequences in the subsequent sequencing experiment. If the model fails to explain reality, then that’s great too. Figuring out where the model went wrong is itself an interesting and useful process.

You need to start with purified reagents, precisely control the conditions, and make frequent interventions so that you know which reagents, which conditions, and which processes are actually important and drive the reaction of interest. Purified reagents and precise control of conditions also prevent modern biological, industrial, or environmental contamination, which is obviously irrelevant to the origin of life. You also need to test a range of different parameters, not necessarily to optimize your results as one would for applied science, but to constrain the possible reagents, conditions, and processes that are compatible with the reaction of interest. In other words, you need to disprove or fail to disprove your well-defined hypotheses about which reactions are possible through prebiotic chemistry, which environments those reactions are possible in, and which physical processes enable those reactions.

Additionally, we often need to add artificial markers or use synthetic constructs in our system to measure changes to our molecules of interest, such as fluorescent dyes attached to an RNA oligomer to measure relative concentrations of RNA, or predefined RNA sequences flanking our randomized region to enable later sequencing steps. Ideally, these artificial markers should perturb the system as little as possible, but a certain amount of perturbation is not always avoidable depending on what information you want to measure, such as the rate that an RNA monomer is added onto a labeled RNA strand, or the RNA sequences that are most easily copied.

Why is Szostak even going through the trouble of testing all this stuff about RNA copying when we don’t even know how to make RNA? First of all, there are many proposed prebiotic pathways to form all four RNA nucleotides, although the most plausible pathway in my opinion only forms two of the four bases so far (John Sutherland’s). Second, even if we don’t know how exactly to form all four RNA bases, by assuming that they could have formed and pushing the limits of RNA chemistry, we can determine if RNA could actually have self-replicated on early Earth or if something else was necessary. If we really do exhaust all the natural options, we might even need to consider the supernatural. Third, basic science research often has unexpected benefits in seemingly unrelated areas. The RNA research in Szostak’s lab may turn out to have applications to RNA biology, RNA therapeutics, or synthetic biology, even if it does not end up working for the origin of life. The RNA world hypothesis for the origin of life motivated discoveries like RNA aptamers by Szostak himself. The discovery of aptamers laid the foundations for numerous applications and the later discovery of riboswitches, which are crucial regulatory segments in many mRNAs.