Of course people could cite the lack of map variety, but in my opinion that is not the actual main reason why sieges are so unenjoyable. I think the reason why sieges are so sub-par in this game is because CA totally levelled the playing field between attacker and defender. Walls should act as a major power multiplier for the defender as when the Turks assaulted Vienna for the second time in 1683, they outnumbered the defenders nearly 10:1 and yet the garrison could hold out for months until the relief force arrived. In this game walls are such a non-factor, if the forces are roughly even, nearly every walled settlement can be taken. Here are the main flaws:
1.Gates are made of tissue paper and can be bashed in by low tier chaff in a more than reasonable time. Actually, they can probably remove the gates even quicker than a battering ram since most infantry is faster than the ram and so arrives at the gates more swiftly. Troops whacking at the gates can also perfectly covered and cannot be affected by defenders behind the wall
SUGGESTION: remove the ability for any non-siege attacker unit to target the gates and double the health of gates. Also, force any unit attacking them to stand far enough outside the gatehouse so it can still be taken under fire from behind the walls
2.Towers have very low, non-AOE base damage, they need to be activated to work at all and they have very narrow fields of fire. All of that makes them near-non factors in sieges. Their DPS is absolutely abysmal and the need to activate them with troops is just cherry on top of the dirt-sundae. Sorry, but if I have to activate towers, I expect them to actually also do damage to attackers but I only really get that if I use the fortification building chain and upgrade it several times. That's nonsensical. Towers should be one of the strongest factors in any siege no matter if upgraded or not.
SUGGESTION: give towers 360° fields of fire and increase base damage considerably
3.Walls don't protect the troops from most skirmisher fire. Practically the only skirmisher fire that troops on walls are protected against are handguns and pistols, everything else curves so conveniently over the walls that the crenelations might as well not exist
SUGGESTION : a flat 75% increase in missile resistance for troops standing on walls
4.Ladders enable all troops to just get over the walls and they don't penalize the troops using them all that much. What's the point of walls (or siege towers) if getting over them is so damn trivial?
SUGGESTION : bring back the old vigor penalties from WH1. Using ladders should be a last resort, not an utter convenience. I know this was probably done because of the gates and forts maps that don't allow the building of siege equipment...but I'd say just restore the old vigor penalty and allow the construction of siege equipment agains such settlements instead. Never made sense to me why it was disable in the first place anyway.
5.Siege towers are too fast and have too much HP. Currently it requires T5 towers plus artillery to stop a siege tower from docking successfully on the walls, after which they cannot be removed and allow easy access for the attacker. This is lame and trivializes walls even if the ladders are nerfed as suggested above.
SUGGESTION: lower siege tower speed and HP, but also speed up their construction. So you can attack with more towers but have to be aware that not all of them will make it to the wall intact
6.Sieges are near mandatory thanks to the extended siege timer. So earlier I'd have asked for the siege timers to be reduced, but I think if the defender is buffed as lined out above, you can also leave the timer as long as it is BUT bring back siege escalation from Attila, 3K and ToB. So a settlement being besieged means the towers and walls will take damage and get destroyed over time just from the fact that they're under siege. So now the choice is to attack in overwhelming numbers to overcome the defenses or to drag the siege out to attack with a defender with more dminished defensive capabilites