HCs are highly effective against infantry and highly-armored units, much moreso than Arbalests, and more population efficient besides.
-No, they aren’t. Pop efficiency is highly, highly overrated, just look at the Goths (one of the best civs in the game statistically.
A much more realistic scenario would be something like, “I built Paladins so my enemy built Halbs. To counter them I then build Hand Cannons, thus not only saving significant time and resources for research, but more efficiently using my population capacity in the post-imperial timeframe where Hand Cannoneers are actually available.”
That’s a not a realistic scenario, in a 1v1 paladins are very hard to get to and taxing on gold, you won’t have much to spare for HCs. In team games, you would just keep making pala and let your teammates deal with the halbs.
HCs aren’t a great counter to eagles either b/c of their lack of speed and ballistics.
People expect HCs to be a very strong counter to infantry as they aren’t that good vs most other units, and they aren’t.