This won't be a popular opinion around here, but I'm not a fan of the EV rebate. I don't think taxpayers should be subsidizing car buyers who can afford $50K - $70K cars. If we really want to solve the EV adoption problem, we should redirect that budget towards improving the charging infrastructure so that Canadians who don't have access to a home charger (e.g. condo dwellers, renters, students, etc) can consider EV ownership without the inconvenience that they experience today.
Even worse is when car manufacturers abuse the program. The latest example is Volvo's soon to be launched EX30. It starts in the US at ~$35K USD, but in Canada, instead of the expected $48K CAD starting price, they priced it at $53,700 knowing that tax payers will subsidize it down to ~$48K. So in other words, tax papers are subsidizing wealthy corporations and their shareholders. Here's
Andrea and Zack Spencer talking about this exact problem.
...but I digress
Regarding your question: should tax payers retroactively subsidize EV buyers? I don't see why they should and I also don't understand why you think you "got screwed".