An excerpt, but the whole is worth considering.
With the shortage of priests in these USA at least, one can see how having deacons who can help with Communion calls and so forth, sacramental prep, service at the altar for solemn worship is desirable. Frankly, I wish I had a couple of permanent deacons around whom I could train up for Solemn Masses. That would make my life a lot easier.
It seem to me that, while priests are existentially necessary for the life of the Church (e.g. Mass, confessions, anointing), and permanent deacons are not in the same way necessary (e.g. they do none of those), having them in service depends a great deal on both the urgency of the need and the quality of formation. That isn’t very definite, I know. First, every cleric ought to be well-formed.
We can’t do without priests, and so we can get on with priests who aren’t so sharp. But we can get along very well without deacons who aren’t so sharp.
Are they necessary? Well… it depends. It depends on if you want to work priests into their early graves and it depends on the level of formation.
Lastly, reception of Holy Orders means that there was a vocation from God to be ordained. We humans can and do get in the middle of that through formation programs, etc. However, God’s involvement means that if permanent deacons are necessary, then they are going, somehow, to be ordained, just as a flower finds purchase and manages to spring up in the crack of a sidewalk. I cannot pass any sort of judgment on God’s role in this matter of the permanent diaconate.
One of the first things that the Apostles did was choose men for the diaconate. That tells us something.
If the same conditions pertain in our day, deacons will be necessary for us just as for the Apostles. Circumstances play a role, and we can discern something of God’s will in the circumstances, as the Apostles did.