The setting max_active_tasks_per_dag seems mostly useless to me / and footgunish.
Why? Because you already have a setting for max active dag runs. If you don't want to run more tasks, don't create the extra dag runs. We also already have a mechanism (param on base operator) for limiting individual tasks across all dag runs where that may be needed. But just a general "i don't want more than 16 tasks running across all dag runs of all types and for all tasks" seems just, imprecise and not useful. I actually think it makes sense to remove this param entirely. But at least we should remove the default. WDYT
