Not with that attitude... Yes you can, there are plenty of ways of comparing regions or countries with high and low vaccination rates, or vaccination uptake. (Of course only while demographically adjusting, but the people who do these studies surprisingly often do think about the basic gotchas.)
The incident of death does increase substantially past 55, however people died at all ages during covid, so we know more infections = more deaths across the board.
Given that the vaccine available at the time resulted in around a 85% reduction in likelyhood of infection, we can for sure declare it saved many more lives than without, unless it directly killed more people than it helped...
Oh man what a gotcha! If only there was some sort of change in circumstances that could impact how many people will die from a new disease, like I don't know, new less damaging variants and significantly better care in facilities that are no longer buckling under the burden of thousands of cases a week.
Haven't heard that before!. Do you have a source to read more about it?
You can't and couldn't possibly know that. Nobody could. What we do know today is that the un-vaccinated aren't dying like was originally claimed they would, in fact they seem to be faring better for those under 60 or so.