Teachers routinely locate and use ready-made lesson plans. Reviewers evaluated more than 300 resources from three online platforms—ReadWriteThink, Share My Lesson, and Teachers Pay Teachers—for alignment to the Common Core State Standards and overall quality. Most of the materials, 64 percent, received an overall rating of very poor or mediocre. In many cases, these supplemental resources are coming from crowdsourced marketplaces, where teachers don't have access to independent reviews of the materials they're downloading.
Polikoff, N., & Dean, J. (2019). The supplemental curriculum bazaar: Is what's on line any good?  New York, NY: Fordham Institute.
https://fordhaminstitute.org/national/research/supplemental-curriculum-bazaar