when do you know it's time to ditch the relational database

hey everyone, i've been wrestling with a design decision lately and wanted to get the community's take. we've been using postgresql for our core application for years, and it's served us well. but as we scale and our data patterns become more complex (think graphs, time series, and large unstructured blobs), i'm starting to wonder when the tipping point is for moving parts of our data storage to specialized databases. are there clear indicators or metrics you look at to decide it's time to move away from a general-purpose rdbms. what has your experience been with polyglot persistence