It's not a 'cut'
First, no one has a legal entitlement to the current schedule of Social Security benefits; Congress can change it at any time. Second, under progressive indexing, the purchasing power of the Social Security benefits received by most workers would rise substantially over the course of the next century. Third, and most importantly, we simply cannot afford the current schedule of benefits. Absent major reforms, the system will default in 2041, and benefit levels will automatically be reduced by roughly 26% for all workers.