That’s not why the RNA world hypothesis was proposed. It was actually first proposed, in 1962 by Alexander Rich, on the basis that RNA serves as an intermediate transcript between DNA and before it’s translation into amino acid sequence.
He merely speculated it might also be able to act as a catalyst. This wasn’t discovered to be true until 1982. It wasn’t until the year 2000 that it was discovered that the ribosome is a ribozyme.
The RNA world hypothesis is supported by numerous different observations, not just that RNA can act as a catalyst and also store information. The fact that RNA either performs or can perform all the critical functions in translation, in addition to serving as an information storage system like it does in RNA viruses (and transiently following transcription from RNA), are just some of these observations.
That nucleotide and nucleobase-derived compounds are frequently used as cofactors in central metabolic reactions (are used as critical “helper” molecules that participate in catalysis by protein enzymes) is thought to be another remnant of the RNA world, and then there’s the fact that RNA monomers are actually chemical precursors of DNA monomers. Basically when cells biosynthesize DNA from the bottom up, they first make RNA and then further modify it into DNA, implying that the pathways for DNA synthesis are later elaborations on the pathways that made RNA first.
The fact that ribosomes are transcribed from DNA doesn’t mean it isn’t evidence for the RNA world hypothesis.
You seem to confuse evidence with proof. That the ribosome is a ribozyme doesn’t prove the RNA world hypothesis, but it’s central roles in translation (not just that peptidyl transferase is a ribozyme) are best explained as byproducts of an earlier stage in life’s evolution where RNA served much more central roles in replication and catalysis.
I don’t think that hypothesis explains all the same facts as well as the RNA world hypothesis does.