From Chris' latest post:

Path of Exile is a game about opting-in to more difficulty in exchange for more rewards

To anyone who's played this game, I think this line is self-evident. All of the game's content follows this theme that you can opt-in to increase difficulty and yield greater rewards.

So it seems hilariously contradictory that they would in the same swoop, move a large amount of the reward away from these opt-in mechanics (all league mechanics fall into this category - Breach, Delirium, Expedition, etc.) and move most of the reward into a very non-optional mechanic, Archnemesis.

If we remove the absurd difficulty scaling of Archnemesis from the equation, you can still see that it's essentially added several extra layers of RNG to the equation that make item drops in general way way more unreliable. Pre 3.19, the majority of a player's important drops would come from opting into as many league mechanics as they could handle. This means running into several of these mechanics in one map, and drops would be generally distributed over all of the monsters killed, noting that rares were much more common back then too. This meant a much more consistent rate of gaining currency, and a much smoother progression for the player.

In the current iteration, opting into these league mechanics is much less rewarding, and most of that reward has been locked behind Archnemesis. Instead of killing hundreds of mobs with greatly increased rarity and quantity in a map, we are forced into killing a handful of rares which again, have several layers of RNG. Firstly, they need to roll an appropriate number of mods. As we've been told, the quantity of rewards greatly increases as you reach 3 and 4 archnemesis mobs. Second, they need to be killable with the combination of Archnem mods and other mods in play, such as essence and map mods. Let's ignore this layer for now, as this argument goes more into Archnem difficulty scaling rather than reward scaling. Third, they need to roll profitable mods. If I get Drought-Bringer, I may as well skip that archnem, because I know all of the rewards will be useless. The chances of me getting Solaris-Touched are so infinitesimal that I could likely run dozens of maps without seeing it once. Finally, assuming this all pans out, I still need to roll well on the drop table to even get good loot.

Adding all these unnecessary layers of RNG to spike loot drops makes the game generally worse to play and progress in. Without even touching the fact that drops are clearly still in a problematic state, even if this system were balanced to offer the same amount of rewards as the previous system (which it's nowhere near), it's an incredibly unfun state to be in.