It's revisionist history to place all of the blame on the Edwin fiasco on the Blue Jays as his agent is easily as much to blame if not more so. Edwin turned down the best offer he ended up seeing in free agency at the behest of his agent. I don't see where the rush to sign Morales in his place came from but that doesn't change the fact that Edwin's decision to turn down the offer ultimately led to him switching organizations.
The 2017 team had enough issues that keeping Edwin wouldn't have been nearly enough to extend the window of contention. Tulo predictably broke for good, Baustista literally became old overnight, Sanchez's career was ruined by blisters, Donaldson started breaking down, Martin was beginning his decline phase etc. The team didn't have a lot of resources left in the minor leagues to trade, there were no young prospects ready to take over for aging veterans, and the payroll was already maxed out so adding more dollars through free agency wasn't much of an option either. The writing was on the wall and the team should have been dismantled then and there.