I discussed this in more detail here:
https://forums.ageofempires.com/t/the-problem-with-balancing-civs-through-missing-technologies/288571?u=cito
I don’t think Mali is a bad design. Its compensation is strong enough that the civ still has a clear identity.
However, Mali helped create a trend: using missing techs as a balance tool.
Missing techs themselves aren’t the problem. Some limitations can create interesting civ identities.
The issue is when too many missing techs are combined with UT replacements, making a civ feel restricted instead of unique.
Cumans are a good example. The problem isn’t just Kipchak missing Bracer. It’s strange when the civ that created a UU can end up with a weaker version than other civs using it.
Cuman Mercs is also interesting, but free ally Kipchaks feel disconnected from AoE2’s normal eco system.
A better solution could be: allies produce Kipchak normally, while Cumans get -25% Kipchak cost from the UT. This keeps the merc theme and also makes the UT useful in 1v1.
My point isn’t that all missing techs should be removed. The problem is when missing techs replace the normal way a civ expresses its identity.