A tricky question. His suggestion that aoe2 could have gone down the cosmetic route is a good one if you could make it work, but I doubt you could. As he says, for a game like this it is essential that users be able to choose for themselves how units look, for readability. But in games where people purchase cosmetics, part of the point is to be able to show that off to other players, is it not? So I don't think cosmetics are as viable a way to fund the game here as they have been for shooters.
With the exception of the latest DLC, I've been a big fan of the approach aoe2 has taken so far. I do like almost all the new civs and new mechanics and new units. But I know many people are getting tired, and it's certainly more difficult to start out today than it would have been 20 years ago. And with the fact that these DLCs are what's been paying for the continued balance & bugfix patches, running the servers, and paying for tournament prize-pools, it's hard to see what other option they could take.