I can't consider anything that is down to average of 50% effectiveness in six months a vaccine...
This is where the 'complex issue' comes in. The data is literally being noticed, acquired, filtered, refined, peer-review, and published on a daily basis.
The vaccine was made for variant "A", and we are on "O" right now. When the dust settles... and it's shown to be 99% effective against "A" at 2-3 years in... can we then call it a vaccine without having to use quotes around the name?
If mumps suddenly mutated to a version that infected 50% of vaccinated people... would we stop calling the MMR vaccine a vaccine? Would a rational person (still 50% effective) not take it?
This _is_ science, and it's HARD. It's nuanced. And the thing you thought was trivial can blow up in your face.
Take antibodies. Some people just don't make them in great numbers. These people are not sickly, nor will they die an early gruesome death. A statistically significant part of the population simply doesn't make them in usable numbers for lots of pathogens, covid included.