Yes, but this need happen only when your data center network is congested, which is hopefully rare and is relatively cheap to fix by adding capacity. And in con

Yes, but this need happen only when your data center network is congested, which is hopefully rare and is relatively cheap to fix by adding capacity. And in congestion cases you need TCP's back off ability. Getting rid of head-of-line blocking also makes messages happen in order. Making messages (sometimes) happen out of order would drastically increase implementation complexity for a lot of apps.