Fair enough I guess, though in that case my mind goes to just having the recipient queue its own tasks internally and respond immediately, if the sender doesn't want to wait on it to finish
If your needs are fairly basic, that's probably the best approach. You also eliminate some overhead (piping messages through a middle man, operating said middle man, etc.).
But it's my understanding that if your needs are a bit more involved, the complexities of building a solid queue mean that it'll take time away from building your actual product. In that case, you may be better served by an off-the-shelf solution which already handles the corner cases and is good to go.
I think this is the usual decision between using an external product and rolling your own.