Because others can say this much better and with better sources and citation than I can, both directly address many of the criticisms made in the essay shared and the faulty reasoning based on it.

International Consensus Statement on ADHD: https://www.russellbarkley.org/factsheets/Consensus2002.pdf

The World Federation of ADHD International Consensus Statement: 208 Evidence-based conclusions about the disorder: https://pubmed.ncbi.nlm.nih.gov/33549739/