What replaced flowcharts? Um, pretty much nothing. We just quit making flowcharts, and we found that we could get by just fine without them. (In fairness, when structured programming replaced goto-based programming, we didn't need flowcharts nearly as often in order to keep track of what was going on.)

We mostly quit doing UML because for most people, most of the time, it mostly wasn't worth it. It didn't provide enough value to be worth the effort. So what replaced it was usually nothing.