Here is a counter-point[1] which finds high levels of lead toxicity in regular citizens. While this article seems to mostly be reasoning based on a literature review, the counterpoint uses analysis of roman skeletons.
That article ends with a note about the source of lead being indeterminate, with a chance the lead leached into human remains after burial.
The issue also isn't just "did they have high lead levels?". The Roman empire around, with its lead pipes, for a long time. Why after hundreds of years would the lead of resulted in the downfall of Rome when Rome had flourished under the same lead-filled conditions previously?
While harder to define, it seems like as time goes on the Roman state apparatus becomes overtaken with people who are more likely to look out for their immediate benefit as opposed to act altruistically for Rome or their immediate community members.
My interpretation of this was the selfless people all died in battle, alternatively it could be the slow buildup of not only the individual but the societal effects of lead poisoning.
Your article seems reasonably persuasive. The thing about the OP is that it's about what the Roman knew - but just any sort of pre-scientific knowledge of poisons tends to neglect questions around long term exposure.
[1]: https://www.chemistryworld.com/news/londinium-romans-blood-l...