This depends on how you're defining containment. Grounding aircraft may not decrease the current case count, you're right, but it may help not adding to it, or adding as much, or as fast. Because of this, it may still be worth doing.
The notion that we're going to abandon containment measures in favor of mitigation, which I've seen in many places (not in your comment though of course), is wrong. We're going to be doing both.
This depends on how you're defining containment. Grounding aircraft may not decrease the current case count, you're right, but it may help not adding to it, or adding as much, or as fast. Because of this, it may still be worth doing.
The notion that we're going to abandon containment measures in favor of mitigation, which I've seen in many places (not in your comment though of course), is wrong. We're going to be doing both.