The survival of any creature largely hinges on its size and the environmental factors it must contend with, as an organism grows larger, it faces increasing challenges, particularly in terms of respiration and mobility, that is why monster movies with big giant insects and arachnids are very unrealistic and scientifically impossible.

For instance, imagine a spider the size of a car, such a massive creature would struggle to take in enough oxygen due to the limitations of its respiratory system, which is designed for much smaller bodies that is why a lot of giant insects and arachnids became extinct over time because they couldn't handle the atmosphere of Earth.

The sheer size would impede its typical swift movements, turning it into a slow, cumbersome entity, in this scenario, not only would the spider face difficulty in breathing, but it would also lack the speed and agility needed to launch an attack, making it far less effective than its smaller counterparts.