CO2 scrubbers don't exist in an economically feasible form. Rather the trick is just ventilation, replace indoor air with ourdoor air. If supermarkets and other public spaces just installed ventilation systems that exchanged their indoor air with outdoors air (preferably with heat exchanges so as to avoid air-conditioning or heating the outdoors), it would absolutely have helped. Ignoring this very interesting study, ventilation still just flat out works to reduce the amount of covid in the air.

Increasing ventilation is unsurprisingly recommended by the CDC, the EPA, and basically every other relevant group. The EPA has a list of papers here if you're interested in scientific measurements backing this (but can I also say it's just common sense?): https://www.epa.gov/indoor-air-quality-iaq/indoor-air-and-co...