It all matters. It's all interrelated. Far too many systems failing, beyond the point of no return.
You are right, the planetary population is unsustainable. But even if that could be mitigated, everything else would still be "wayyyy in the red", and no way to pay the bill.
Natural systems are failing now, and human systems won't be far behind. Far sooner than anyone dares to imagine.
That said, electric cars aren't going to "solve" anything, just slow it down just a bit. CO2 absolutely matters, but electric cars aren't going to address all of the other sources.
So drive what you like and enjoy yourself while you can!