BBR is not magic
BBR is a model-based congestion control algorithm. It estimates the bottleneck bandwidth and round-trip time, then paces packets against that model instead of reacting to loss. On long, lossy paths it is a genuine improvement.
On a shallow-buffered access link shared with a dozen long-lived flows, it is noticeably worse than CUBIC — it fills the buffer, induces standing queue, and increases latency for everything else. The model does not know what it does not measure.
Enable it when your users are far away and your paths are clean. Leave it off on
the last mile. Measure with ss -ti rather than vibes:
ss -tin dst 10.0.0.0/8 | head -20