I don't think you need an 8 ball to predict that you shouldn't travel during this global pandemic -- especially in the past 6 months when it's all hit the fan.
Now they are in countries in the Caribbean that have managed the virus relatively well and are overloading their public health system because they urgently need tests. Canada is just creating a problem for poorer countries while gaining very little - there's barely any community spread. If a Canadian returns home from the Carribean, on average both countries will have less covid.
Governments has been telling people for months not to go on vacation, that is correct, they should have thought of that before leaving.
They also gave 2 weeks notice so if you went somewhere and didn't think you could get a COVID test, there was still time to make it back home before the ban started.
If only these people would suffer that would be alright - it was their mistake. But rich countries should not make poorer countries pay for the bad decisions of their own citizens. Policy needs to be guided by data, not emotions.
That's their problem. Should have thought of that before going on vacation, etc.