Well, yeah, because those have an appropriate amount of horsepower under the hood.

My mum's car at that point must've been a first-generation Opel Meriva: https://en.wikipedia.org/wiki/Opel_Meriva#First_generation_(2003)

In the back of my head, I did also have this tidbit:

The first generation, named "Meriva A", was based on the third generation Opel Corsa C.

So, take a car frame with the weight and height of a family van and put it onto the powertrain of a small car.

Like, genuinely, I'm finding Meriva's being sold online with 75 horsepower, which is as much as the Opel Corsa had back then.
The Corsa wasn't exactly known as a sports car either, so I'm really not surprised that its family van edition can't accelerate. 😐