Observations of the cosmic microwave background provide a rich dataset, probing a diverse set of fundamental physics in both the early and late universe. CMB measurements are a cornerstone of our now exceptionally precise Lambda-CDM model of cosmology, however, many questions remain. Recent technological advances have enabled increasingly sensitive experiments focused on measuring the faint CMB polarization. These data target cosmological physics that expands on the standard six-parameters, including the signals from an inflationary epoch and effects of neutrinos. One such experiment is the latest receiver on the South Pole Telescope, known as SPT-3G, which began a five-year survey of the CMB in 2018. This millimeter-wavelength receiver contains a focal plane of approximately 16,000 polarization-sensitive superconducting detectors distributed between three frequency bands. I will discuss the technological challenges presented by the SPT-3G detectors and readout and the advances that led to an order of magnitude leap in total instrumental sensitivity. I will also introduce CMB-S4, an upcoming set of ground-based CMB telescopes that will make the next dramatic leap in the sensitivity, and provide some perspectives on the opportunites for superconducting detector and readout technologies.