You are correct that the concept of particles in physics is a useful representation or model of our current understanding of the universe. In modern physics, fields are indeed considered fundamental, and particles can be understood as excitations or quanta of these underlying fields. This viewpoint is particularly emphasized in quantum field theory, which describes the behavior of elementary particles and their interactions.
According to quantum field theory, the fundamental entities of nature are not point-like particles but rather fields that permeate all of space. These fields are associated with different types of particles. For example, the electromagnetic field is associated with photons, the electron field is associated with electrons, and so on.
Particles can be thought of as localized excitations or disturbances in these fields. When a field is excited, it manifests itself as a particle with certain properties such as mass, charge, and spin. In this context, particles can be understood as the quantized units or "packets" of energy and momentum that emerge from the underlying fields.
So, the understanding that fields, rather than particles, are the fundamental building blocks of the universe reflects the idea that particles are not discrete, isolated entities but rather manifestations of underlying fields that extend throughout space. This perspective helps in reconciling the behavior of particles with the principles of quantum mechanics and provides a more comprehensive framework for understanding the fundamental nature of the universe.