No, what ID says is that the most rational belief is the belief in a designer.
...for which we have no scientific evidence and no even plausible mechanism for implementing the design (other than 'poof!'). I don't think so.
There are plenty of reasons not to believe in an RNA world -- RNA is delicate etc. -- but you do.
RNA isn't that delicate. The main reason it hydrolyses easily in a lab is the ubiquity of nuclease enzymes - which obviously weren't a problem in prebiotic environments. Cytoplasmic ribosomes, for example, whcih are largely composed of RNA, have lifetimes of several days. I've listed already the reasons why I think RNA preceded DNA as the genetic material, although I don't think it was the original self-replicating material.
There is no scientific evidence for RNA world. RNA has never been seen evolving into DNA. No naturally occurring RNA molecules have been found that direct the replication of other RNA molecules. It's all supposition.
and no even plausible mechanism for implementing the design (other than 'poof!').
Well, no it would be a force unknown implementing the design. Sort of like how RNA would switch roles with DNA.
The main reason it hydrolyses easily in a lab is the ubiquity of nuclease enzymes - which obviously weren't a problem in prebiotic environments.
The prebiotic envirnoment is still subject to debate. Even without hydrolysis, RNA breaks down from background radiation. Anyway, the lack of enzymes is also a stumbling block. Without protein enzymes, researchers have not been able to produce a duplicate of a RNA template.