I don’t think you’re wrong. Evidence is in the form of Mr Polarized himself not doing Z2 + 4x8 (or 4x4 or 4x16) all year long every year. I don’t think you’d be a well rounded cyclist following a protocol like this all season long. Does anyone hate themselves that much to attempt it?
You’re not wrong that a bunch of people including TR don’t understand polarized training, or at least not applying it based on the science. For example seiler found mixing intervals types within a block provides less gains than doing blocks of similar intervals repeatedly in a periodized manner