Improving Seniors' Timely Access to Care Act of 2021 This bill establishes several requirements and standards relating to prior authorization processes under Medicare Advantage (MA) plans. Specifically, MA plans must (1) establish an electronic prior authorization program that meets specified standards, including the ability to provide real-time decisions in response to requests for items and services that are routinely approved; (2) annually publish specified prior authorization information, including the percentage of requests approved and the average response time; and (3) meet other standards, as set by the Centers for Medicare & Medicaid Services, relating to the quality and timeliness of prior authorization determinations.