There is a unit in the more recent civs added to Age of Empires 2 that completely sums up the issue with MAs right now (Because MCs are not overpowered in any way at this moment).
The
Konnik is a unit that starts as a cavalry unit, and when it "dies" it is transformed into an infantry unit. That's one of the biggest issues with how MA's currently work. All you need to convert foot fighter (which should already have 100 archery) to an MA, is 100 Controlled Riding, 100 Mounted Archery, 26 Creature Control. It turns MAs into a two phase bossfight with them becoming formidable FFs the moment their mount goes down.
That means for 226 points (Minus attribute / clade bonuses) you can make a foot fighter into a damn near fully proficient MA. Because lets be real, you don't need those 300 points of additional archery skills to be 99% effective at archery. If they actually needed to spec 400 points archery to really be fully viable with a bow they would have to make some big sacrifices though.
And that's where I would address the entire issue. The archery tree is not well set up, and fixing archery could help the issue massively.
1. MAs and Footarchers get way too MUCH value for 100 points into the archery tree.
2. MAs and Footarchers get way too LITTLE value for 400 points into the archery tree.
3. Longbows are not as strong as they should be as the only bow that can't be used while mounted.
Fix those three things and I think the MA issue would largely be addressed once some other root causes like troop transportation are handled. Basically, buff a 400 point archer build, nerf a 100 point archer build, and increase the power of longbowmen above all other bow types if you full spec archery.