I'd say they have been excellent in terms of the farm system (drafting, international signings), but the one knock on them has been MLB transactions. Those have been a mixed bag, made worse by some bad timing with trades (JD, Osuna, Happ). I guess you could argue had they started the rebuild during the 2017 trade deadline or prior to the 2018 season rather than at the 2018 trade deadline that maybe there would be some better young pieces in the pipeline to go along with the existing top farm system, but hard to say without knowing what exactly they turned down in 2017-18.
Considering the situation they inherited, an old playoff team with essentially a one year window, I'd say they did pretty well all things considered. It's much easier to acquire vets in free agency/trade in today's market than it is to develop stars, and the Jays have the potential to develop some stars in the next few years, as early as 2020 if the season starts/concludes.