Just watched A Bug's Life with my kid... This scene is always relevant.

two main reasons: one is that they were smart about what to tackle considering graphic capabilities of the time, for example toy story is a perfect first movie since everything looked plasticky at the time, so a movie made almost entirely of toys and furniture wouldn't look so bad.

second is that they worked on their rendering engine specifically for what they wanted to create, so for a bug's life they created the subdivision technique which is still an incredibly prevalent method to create smooth curved surfaces.

it also allowed them to model the squishy caterpillar, but again they were smart about their capabilities so they limited the soft body to that character and made the rest hard shelled insects like ants, grasshoppers, a stick bug, etc.

I don't know this for a fact but they also probably worked on linked objects which allows multiple instances of a model to be reused without making your ram explode: the movie is full of things that are numerous: grains, rocks, leaves, grass, even the ants themselves.

finally lighting goes a long way to make things look good. every movie they made had great leaps in terms of lighting.

smart movie making decisions can make movies timeless.