Thanks for sharing your experience. I think this problem of wild-vs-cultivated plants is a major data quality issue for iNaturalist. The general disregard for logging establishment means was shocking to me when I first logged on to iNaturalist. iNaturalist could be a great tool for tracking biological invasions, but instead, as you’ve noted, it ends up being mostly useless in that regard because so many users upload cultivated plants without marking them as such.
But this concern is not universal. Some people think it’s just not a big deal to have a bunch of garden plants undifferentiated on the site and others oppose seemingly any change to the uploading process, even changes that don’t require extra steps (unlike e.g. the pop-up referenced above in this thread), preferring to shunt the workload of marking things cultivated onto others. To read some of these viewpoints see some responses to my proposal for separate “wild upload” and “not wild upload” buttons here: