The Hero's Path

Archangels are powerful units, so they had to be given out after completing significant tasks. They are more like a bonus than a full-fledged combat unit. From a developer's perspective, level 7 creatures are too durable, which means the player doesn't lose them easily, which means they spend less money replenishing their army, which means they accumulate wealth and cause a kind of inflation in the game. If I were making a new map, I would even give level 6 creatures much later, to increase the army turnover.

The problem is that some other, equally durable level 7 creatures are available much earlier, and their numbers can be accumulated much faster than when the player reaches the point of obtaining the Ash Tears and using them to buy Emerald Dragons or Archangels. Cyclops are available from the Wyvern trader around 20% of the way through the game, Phantom Dragons (if the player is a Necromancer and wants to reach the location, they will easily find them), Devils (similarly), and even for Magma Dragons, as far as I understand, it's enough to build a Guild of Mages (a task that isn't easy, of course, but it's still clearly earlier than obtaining the Ash Tears). And here you have the Ash Tears in your pocket, you've already completed almost all the main quests - and only then are you given the long-awaited Archangels.