Understanding the chemistry and physics of polymer systems challenges scientists from a wide spectrum of research areas, ranging from polymer science to molecular electronic structure theory. One of the characteristic features of polymer systems is that their physics involve a multitude of different length and time scales, which generally render the determination of their structure and physical properties on a detailed level computationally exhaustive. To overcome this difficulty, novel field-theoretic methodologies based on the mean field approximation have emerged recently and have proven to deliver useful results in the calculation of mesoscopic polymer models in the regime of high monomer concentrations. In this review we demonstrate that the field-theoretic approach is not only an useful formalism for treating highly concentrated polymer systems on the mesoscopic level of description, but that it is also a promising theoretical tool, to solve the multiscale problems arising in the calculation of physical properties of a wide variety of neutral and charged polymer materials. To this end, we show that the field-theoretic approach possesses the advantageous property to enable the treatment of all levels of description, spanning from the quantum to the continuum scale, within an unified theoretical framework. On the example of the coupling of the mesoscopic and continuum scale, we show that this specific feature constitutes a crucial advantage of field-theoretic approaches with regard to current state-of-the-art particle-based simulation methodologies for connecting different levels of description. Another major benefit relates to their favorable approximation characteristics, which permit to devise efficient approximation strategies for evaluating sophisticated polymer solution models in the low to moderate regime of monomer concentrations in a reliable way. To show this, we present novel low-cost approximation strategies beyond the mean field level of approximation using effective renormalization concepts, originating from the domain of quantum field theory, and demonstrate their usefulness in the calculation of structure and physical properties of several polymer models, described at various levels of description.