Active polling scales _better_ than the alternative. You directly manage the ingest rate at the server side, rather than DDOSing your monitoring infrastructure when you scale out your services to deal with load.
Why in the world would you want to manage (which I'm reading as throttle) the ingest rate of a monitoring service? That strikes me as a recipe for missing important events.
Monitoring should be a fairly stable load rate. If you're setting up monitoring, and your machine can't handle the load of all the data points coming in, you need to shard out, not drop data points.
> Active polling scales _better_ than the alternative
Exceptional claims require exceptional evidence. Personally, I have never heard of anything that is actively pinging outside services performing better than receiving and processing data passively.
Prometheus will scale better than Nagios running active checks since it won't be using subprocesses, but it is still going to require more overhead than a service receiving passive reports.
A single big Prometheus server can easily do millions of time series, and in an older record, 800,000 samples stored per second. You could monitor e.g. 10,000 hosts with that with quite some detail, and the bottleneck is still not the pull aspect.