Yeah I wasn't a fan of the Dickey trade at the time it happened as well. AA's worst trade for sure. Thought the Jays bought high on a 38-year-old knuckleballer coming off an NL Cy Young. Plus the Jays had to f***ing roster Josh Thole lol. Dickey wasn't anything special during his time with the Jays, but he was consistent and reliable in terms of making his 33-34 starts and pitching over 200 innings. Still, missing out on the seasons Syndergaard had in 2015 and 2016 really hurts. Imagine in 2016 a rotation with Syndergaard, Stroman and Sanchez. Even in 2018 and 2019, Thor posted 4 WAR seasons so he was still a valuable asset. Travis d'Arnaud was solid in 2014 and 2015 as well. Jays got hosed.
I still think Varsho could be a solid player. Like you said, the trade overall may never be a net positive but as long as Varsho can give the Jays 3-4 WAR seasons moving forward with excellent defense in CF, he'll help this team over the next 2-3 seasons.