There are units that are countered by infantry, cavalry or archers. If aa civ is countered by one of these, that’s bad game design. There are very few civs which are just countered by cavalry, infantry or archers. Burmese, Gurjaras and Hindustanis during specific ages are the only ones I can think of.
Not sure why you are saying this. This has nothing to do with anything.
Firstly, I don’t think variety is not always good. In fact, I made an entire thread explaining why it is not. LINK.
Two, if you don’t like shrivamshas and you didn’t complain, that’s cool. But that says nothing broadly. People might like it or entirely reject it. Others don’t have to share that attitude.
I assume that you are talking about Centurions here. This is extremely dependent on the situation. If we are playing closed maps, I’ll go for a scorpion-centurion combo early, and add in legionaries later. I’ll ignore centurion armour upgrades if you have halbs. There are like 4 plays here usually, in my experience. Not going to write all of those now. But the point is, you don’t need many blacksmith upgades. None for archers, only 2 for infantry armour and 3 for melee attack.
I don’t get what you are saying here. So what if it’s 2/3 gold? Your composition as a different civ could be 1/3 gold comp, but you spend 3 times as much as gold.
Hypothetically, there could be a civ which has 3 unit lines all of which cost 5 gold per unit. This civ could now do full gold comps, and last longer than you fielding just one gold unit.
Heck, Portuguese with their feitorias can last forever fielding all gold units if the opponent plays badly enough.
It’s about income and expense, not what fraction costs gold.