I think Liereyy was talking about this a few days ago, Sicilians got way overbuffed.
The core issue with them is that they have the widest tech tree in the game (beating Byzantines at this point), AND most of their units beat their counter units too decisively.
Even other pros, like DauT, have admitted that they are “broken in some matchups” (and just generically “strong” in most of the remaining ones).
Their only flaw is a lack of an eco bonus before Castle Age, but even then, with the wall meta, that’s not very relevant and means that you as the opponent of the Sicilians MUST do damage before Castle age, which is very map- and player-dependent, and overall, it’s not something entirely under your control (meaning that it’s a mix of luck & opponent making mistakes & you hitting good timings whether you find any Feudal damage).
More specifically, the opponent can make some of the following units vs the Sicilians, but all have counters:
Skirms? Sicilians can just make their own Skirms and outtrade you due to dmg reduction. At this point, I think only Byzantine Skirms make sense vs Sicilian Skirms, and with any other civ, if you see Sicilians making Skirms, you should do some unit other than Skirms to counter them.
Pikes are a no-go vs Sicilian Knights due to their dmg resistance, and Monks only work in early Castle Age vs small numbers. Sicilian Knight all-in in early Castle, if the Sicilian player is even slightly ahead, is very hard to stop.
the Sicilian player can also aggressively go Crossbows in Castle Age, and its natural counter unit, Skirms, does less bonus dmg. Skirms doing less bonus dmg to Crossbows is actually significant and it takes noticeably more hits to kill a Sicilian Crossbow than a generic Crossbow (didn’t do the math, but intuitively based on ingame observations about +40% hits required). Sicilian Crossbows are surprisingly good, and also a long-term viable unit due to Arbalest upgrade. Likewise, the lack of last armor is more or less offset by the dmg resistance, and though the lack of Thumb Ring means it’s not a viable unit in super late Imperial age, it’s “good enough” to matter for most of the game (let’s say it’s good roughly until ~50 min into the game, and after, you can probably transition out of it).
Sicilians have FU Halbs who take less dmg from Skirmishers (Halb + Siege Ram is an above average comp for them compared to generic Halb + Siege ram).
The unique unit, particularly the Elite upgrade is (in my opinion) a bit too good. 4 + 4 Pierce armor is nuts and makes it very resilient and allows for a good flood.
Of course the big elephant in the room is Hauberk Cavalier, who is a hard counter to all Archer civs (Britons, Ethiopians), but also to Meso civs who just die to it.
Although until early Castle, Sicilians lack an eco bonus, the extra +100 stone gives you the option to go for a 4 TC boom (remember that above all, TC is a defensive building), or do Donjon defense on gold in Feudal age + 2 TC boom right after. The Farm bonus also kicks in after a while and translates to some wood savings at around ~30 min, which though not as impactful as some of the more early game bonuses (say Franks) is a good bonus nonetheless.
Anyway, the core issue is that Sicilians army composition is too strong. The direct comparison for them would be Byzantines, who lack an eco bonus and compensate for this with an (allegedly) wide tech tree. Sicilians need to have some unit that they are not allowed to play given the (very strong) bonus of military units having damage resistance. Currently, they can play infantry (full Barracks), Archers (Arbalest with Bracer and dmg resistance), Knights (one of the better Knight civs in the game), rly good Siege workshop. Really you can’t go wrong with ANY opening as Sicilians, they only lack Bombard Cannon to be able to do anything.
My proposal would be to tone down their Archery Range (they are an “infantry & cavalry civ” after all), some ideas would be:
a) remove Bracer
b) remove Arbalest upgrade
c) remove 2nd archer armor (making them similar to Burmese)
d) Archery Range units excluded from dmg reduction bonus.
This way, there would be more windows to punish Sicilians, currently, if you haven’t done any damage to them by, say, minute 25, they can make any unit and outvalue anything you make always.