I think some of the reasoning about aluminum is a bit ridiculous because aluminum has its advantages over carbon but people are not discussing this due to their extreme bias.
The simple advantage of aluminum is lower cost than carbon. Because of this, I think there is a place for aluminum as a lower cost beginner hydrofoil. As hydrofoiling continues to grow in interest, I have been surprised no-one has offered such a product to grow the sport.
The makers of boat hydrofoils have done this. For example, here is a complete hydrofoil with board for $750. This new/small manufacturer sells directly on eBay.
An advantage with aluminum is it can be extruded, which will lower the cost even more. For example, if the riser is made of a symmetrical NACA extrusion and a wing from another un-symmetrical NACA extrusion, this would save much machining cost.
I feel for hydrofoiling to grow, there has to be a low cost beginner product. In fact, one boat hydrofoil manufacturer has realized this. As a result, if you buy a beginner hydrofoil from them, they offer a trade-in program if you want to upgrade to a more expensive model within a year from the initial purchase.
For this sport to grow, I think we need to have manufacturers that will open their mind toward using the advantages of metals and carbon. Each has its place.