Asklemmy

Could be either, depending how you write it.

Lean into the creepy factor and ramp up the anxiety by adding recent events found in the tape and a feeling of en-ease as they're discovered. Deja vu can solidify it further, causing chills down the spine. Add an event that is then found on the tape before it happens, proving it's a prediction. As the tape is repaired, more is discovered. Your indication of progress is how much tape is left to repair, providing a mystery, and anxiety, of what will be found next.

Lean into the sad factor by showing the world now and reminiscing on the lost. Ramp it up with something the character loved, maybe shown in the tape, and then showing the last of it going away. Add in the nice old man, the character's savior, dying; not from age, but because of the destruction. Could show malnourished children, though that can be triggering. Showing malnourished animals would give a strong visceral reaction without having the same trigger. Be careful going too far in this direction as it can quickly become depression porn. You'd need to have a ray of hope or something the character is fighting for. The tape could help if it's shown to have accurate predictions. It could show a happy, green field, blue sky, kids playing type thing at the end. This could give the character hope.

Another layer of sadness would then be an oscillation between believing in the happy prediction or not. To ramp that up, show one tape prediction as false, or presumed to be false to the character though actually true. (Think Shrek 2 when he thinks the potion is a dud until the next morning, though the audience sees it worked after he turned away). It'd be up to you to determine if the final hope is true or not, letting you end on a high note, or a low one. Either way could be impactful.

Overall, it's a fun premise which you can take in many directions.