The IceCube neutrino observatory has established the existence of an astrophysical diffuse neutrino component above $\sim100$ TeV. This discovery was made using the high-energy starting event sample, which uses the outer layer of instrumented volume as a veto to significantly reduce atmospheric background. We present the latest astrophysical neutrino flux measurement using high-energy starting events. This latest iteration of the analysis extends the sample by $1.5$ years for a total of $7.5$, updates the event properties with newer models of light transport in the glacial ice, and has an improved systematic treatment. As part of this new analysis, we report on compatibility of our observations with detailed isotropic flux models proposed in the literature as well as the standard generic models such as single, double power-law scenarios. We find that none of the tested models are substantially preferred with respect to a single power law.