being able to withstand whatever other meta/high tier civs generally go for strategy-wise and counteract to that.
For example, if Magyars were meta, being able to mitigate their 19 pop Scouts would be important in order to be a “balanced, good civ”. Of course same considerations apply to their early Castle age Knights flood/all-in.
Mind you, when I say “mitigate”, I don’t mean only having the right counter units (e.g. Japanese Halberdier to counter Frankish Paladin), I also mean not falling behind in the game in general. All too often, some civs CAN do the right army composition or strategy, BUT they “get there” too late where it doesn’t matter. Brilliant example being Spanish who have insane compositions in theory and all the counter units that you can hope for, but just can never get as competitive and “fair” fights because due to lacking eco bonus, for example when you push out 4 Knights, the enemy has already 6-8 (because they have a slightly faster Castle age time due to having e.g. Frankish berries).
Stuff like this matters a ton in high elo where tech transitions and countering are not only about choosing the right unit but also about having enough time and economy to mass enough relevant units. The game is half about having the right units and half about timing and transitions but also knowing when you are ALLOWED to transition without dying.
Low elo players fail to grasp this incredibly hard, for example when I play vs 1000 elo players and they are, say, Mongols, they systematically go to Stone at the 15-16 min mark (sometimes even earlier) because they hope to build a Castle and get out Mangudai which is a rly good power unit. Their linear approach to the game makes them think that even if they take some damage, Mangudai will make them recover *that can be true), but more importantly that I will somehow let them. In low elo this works very often because such greed is generally unpunished, but I generally punish it instead. In the specific case, by putting ~5 vills to Stone (1/6 of your economy in Feudal), my opponent hits Castle Age 1-2 min later. I then do either 3 TC boom right away and get to Imp first, or more commonly all in him with Knights just as he hits Castle age. It is really really to sustain the pressure if I already have 6-8 Knights when you are making your first ones or first Camels. Even if he makes counter units, I will add Scorpions, Monks etc.This of course on top of me scouting for the foundation of the Castle and trying to kill as many Vills as possible if not deny it altogether.
This is why in the case of Mangudai, for example, you generally go for it AFTER you did damage to the opponent or took a lead, Stone is a HORRIBLE resource to gather if it’s an even game because the Castle can’t move around the map and building a Castle means a lot of lost eco, on top of not being “incremental” in the sense that with day Gold, every 75g gathered you get a small reward in the form of a new Knight that you can use immediately, with Stone you must float 650 Stone before even building a Castle and 649 and 0 Stone are practically the same in terms of game outcome.