plot items so bad they destroy the series in hindsight

[Deledrius]

If TNG was a series that was really strict about continuity, instead of conveniently forgetting series-breaking fixes, then the straw that would have broken the camel's back would have been "Unnatural Selection" S2E7. Pulaski's dying of rapid aging caused by some genetically engineered test-tube children, but they're able to cure her by taking a weeks-old sample of her DNA and using the transporter to reset her physiology to before she was infected, but she keeps all the memories of the intervening period. How could you ever have drama surrounding illness or aging if you can just constantly reset yourself to an earlier state? People complained about Khan's magic blood in <i>Star Trek Into Darkness</i>, but this was worse. (I know there are other SF works where this kind of instant backup is common, but it would drastically alter the setting of Star Trek.) Luckily, this technique is never brought up again.

I don't even comprehend writing a conclusion like that and not realizing that it breaks everything.