considering how attached Grinding Gear Games seems to be to the Mirror idea

Yeah. So rather keep as is? What should have Grinding Gear Games done instead? What is "the solution to the problem"?

That's exactly the point he was making. The only league where eternals were making a serious impact with regard to "6 T1" items are the permanent leagues. Temp leagues simply don't go long enough where many people seriously try crafting 6 T1 items and profit off repeatedly mirroring them.

The richest people are those with 6T1 items already and the available currency to use up the remaining eternals to create another 6 T1 item.

So in effect all this does is monopolize the 6T1 items into the hands of people who are already very rich.

Eternals are bad for the game conceptually, but just suddenly stopping their drop rate here is rather inelegant and doesn't really fix the problem.

I'd rather see them remove mirrors and increase the drop rate of exalts and eternals, to be perfectly honest. But that doesn't seem likely considering how attached GGG seems to be to the Mirror idea, and how they have their logo with a mirror on it.

Alternatively, they can remove Eternals, increase the Exalt drop rate (so it can be used by more than the uber rich), and slightly buff the mirror drop rate to reflect the fact that they are no longer equal to the best possible rolled rare in the game.

Alternatively, there are other creative solutions mentioned by others in this thread, such as making it so a mirror cannot be used on an item that has been restored by an eternal, or using a mirror makes one duplicate of the item and then both items become mirrors, so the goal of eternals doesn't become "be hilariously rich, craft a 6 T1 to get even richer".

It could also potentially reduce the value of mirrors, as they no longer represent a 6T1 GG perfect rare. I wouldn't mind a slight buff to their drop rate (i.e. you still would never see one) to correlate with their small diminishment in value.