You can remove Bombard Towers but never Cannon Galleons. They aren’t strong, slow projectiles, slow fire rate. Maybe attack buff doesn’t effect them makes sense if you are trying to balance water-land.
Why bombard towers exist? I couldn’t find any information on Google, just Age of Empires 2 results.
A number of things:
#1. A generic bombard cannon gets 12 range. With Siege Engineers (if the civilization has it), this becomes 12+1.
#2. A Turkish bombard cannon starts with 12 but ends with 12+2 once Artillery tech is researched.
#3. Castles and Towers get 8+3 range assuming they get Bracer.
#4. Some civilizations get unique techs/bonuses(depending on the version of the game) to increase the range on their Keeps(Koreans)/Bombard Towers(Turks)/Castles(Teutons) by another 2. This helps them to return fire against non-elite cannon galleons (except those with Artillery tech), Bombard cannons (even those with Siege Engineers), Fully upgraded British longbowmen (12 range)
#5. So, at 14 range, your Bombard Cannons outrange all defensive buildings including those with special bonuses/techs, non-elite Cannon Galleons and Fully upgraded Longbowmen. They’re only outranged by elite Cannon Galleons and Trebuchets - Neither of these units is really good at taking out units unless you’re talking about Spanish Elite Cannon Galleons or British Warwolf Trebuchets.
#6. Apart from all this, One extra range is huge on closed maps like Michi, Black Forest where siege dominates. It helps you fire at enemy siege before you are within their range and helps you take out forward Bombard towers by enemies.
#7. 14 range means they’re that much better at taking out enemy Siege Onagers. Korean Siege onagers used to have 12 range which got nerfed to 11 and is now, 10. You have 4 range more than these while most Bombard Cannons got 2 or at the most 3.
I think the above points demonstrate the sheer utility of Turkish Bombard Cannons that damage output is not always more important than range and HP.
Turkish Cannons benefit from a range of bonuses, Free chemistry, 20% faster creation rate, 25% extra HP (lets them survive a Siege Onager shot), Artillery tech which gives them +2 range.
IMHO, as for Bombard Cannons,
#1. Turks
#2. Civilizations with Siege Engineers and maybe some bonus/tech that is not so good like Portuguese, Teutons.
#3. Italians
#4. Civilizations with Siege Engineers (Koreans, Indians, Franks, etc) but no bonus
#5. Spanish
#6. Civilizations without Siege Engineers
Apart from this, the Artillery tech also buffs Bombard Towers and Cannon Galleons. Your Bombard Towers can return fire to all enemy non-Turkish Bombard Cannons and non-elite Cannon Galleons (assuming they’re not buffed by the Artillery tech), fully upgraded Longbowmen. The only other buildings that can do these are Teutonic Castles with their Crenellations tech and the Koreans with their Eupseong… Apart from this, Free chemistry and cheaper gunpowder techs helps as well.
Turkish Bombard Cannons have been the best in the game right from the start. The only time they were not #1 was when the Portuguese Arquebus tech was overpowered for about 1.5 years. After that, it has been nerfed into oblivion.
Turkish Bombard Towers are top tier, just like those of the Koreans, (Free tech, faster stone mining, previously 25% faster building which added upto 45% with Treadmill Crane) the Chinese (30% extra HP but with Masonry and Architecture), Byzantines (40% extra HP without Masonry and Architecture), Spanish (30% faster building, Supremacy tech that helps forward building). I would even say they are better than most if not all those mentioned in this list.
As for Cannon Galleons, their non-elite Cannon Galleons can outrange all defensive buildings (even those with special bonuses/techs to improve range). Their Elite Cannon Galleons get 15+2 range which is tied with the non-Tatar trebuchet for the 2nd longest ranged unit in the game. In ship vs ship combat, this is not HUGE, though. In Ship vs Ship combat, the Spanish Cannon Galleon is far superior any day. However, the Turks also benefit from 20% faster creation speed, free chemistry and 25% extra HP which are not HUGE for Cannon Galleons but nice to have.
To conclude, this tech ensures your Bombard Cannons, Bombard Towers and Cannon Galleons outranged by anyone other than those of another Turk or Trebuchets (especially with Siege Engineers and/or Timurid Siege Craft). This is far superior to having Siege Engineers (+1 range and +20 attack bonus).
Do they, though? I mostly lost to Vikings once they hit Castle Age. I was playing as the Portuguese. However, in the late Imperial age, Vikings couldn’t fight back against massed Caravels.