I'd suggest the hubris is in the author identifying as a "Ratonalist", cherry-picking the others whom he identifies as being in that same tent, and identifying with them while simultaneously declaring their efforts trivial, and over-emphasising quantitative measures at the expense of social considerations.
It's more evident in the comments on that page. From the author:
"I heard that the Moderna vaccine was designed in two days... But the deeper point which this is trying to operationalize is 'vaccine design just isn't that hard', in the sense that we don't need to test many designs to find one which works."
He seeks to demonstrate that an individual can 'operationalize' a vaccine i.e. manufacture personal doses. He describes his motivations: "we've all been complaining about how 'we' (i.e. society) should [make vaccines and tests], yet to a large extent they’re things which we can do for ourselves unilaterally" and says he hopes his efforts are "enough to go out, socialize, and generally enjoy life without worrying about COVID."
There's little consideration of 'should' only 'can'. Is it desirable to have people self-vaccinating then socialising? What might go wrong, and how might issues be mitigated? Are there broader issues with showing how to order items from Amazon then snort them in the name of self-vaccination?
I'm also unclear of the evidence supporting his assertion that these are things "we can do for ourselves".
His other motivations include this being "a fun project" and "build[ing] the habit of Doing This Sort Of Thing, so next time I hopefully do better". His self-awarded "D" grade is assigned on the basis that he is "embarrassed" at taking 4 months to notice radvac. He refers to this as poor "performance", but I'm not sure what performance is being measured: reading a news-feed or developing lab-skills?
He draws a lineage from "Benjamin Jesty, the dairy farmer who successfully immunized his wife and kids against smallpox the same year that King Louis XV of France died of the disease" through to himself, in the name of "Rationalism".
He describes his experience of the pandemic as "a near-perfect real world equivalent [of Jesty's experience] on super-easy mode with most of the work already done by somebody else". This makes his detailed description of the process he followed feel like a bald-faced humble-brag to me: here's all the juicy detail; I consider this to be 'super-easy mode'. I recognise that it might be self-deprecation and a recognition of standing on the shoulders of giants, but that just doesn't come across for me.
To be frank, and I recognise how subjective this is, the entire exercise whiffs of self-aggrandisement. A less contentious approach might have been to do the work anonymously and post on a pre-print server that permits anonymous papers, then optionally de-anonymise once results are collected.
The whole approach just rubs me the wrong way, and the "Rationalist" declaration exacerbates that.
At least he does mention the problem with expertise: "you need some level of expertise yourself before you can distinguish real experts from fake. There is no substitute for learning at least some amount oneself".