Except the engine would only be a good comparison if we were talking about something like the speed of the game. Weapons modifiers are hardly as essential to the game as the functioning of the engine is to a car. Not only do people use overexagerated terms, we are now also using overexagerated metaphores.
Aside from that the proof that weapons modifiers are bugged has just been countered by a dev. Shows why data should be provided with claims because then we can either confirm or counter the conclusion. But we all know hardly anyone will anyway.
Only comparing the engine of a car to the speed of the game is rather silly. The engine is a very important part of a car, just like the combat system is important to the game. If it isn't working as intended, it's perfectly fine to call it broken. You are just nitpicking. Instead of addressing the real issues, you are attacking the use of a single word, and aren't really contributing to the discussion. The issues stay the same whether or not anyone use the word "broken".
Also, the dev did not counter anything, other than stating you get no bonus damage from tech when fighting rebels. This also applies when fighting against similarly advanced nations, but you still get a defensive modifier from other stats. This means that defense will increase over time, while offense will not. This is the issue. You can accept it as breaking or not, but the fact remains, that it has profound effects on late game combat.
Having to defeat the same low moral army 10+ times for it to finally die, cannot be intended, and warfare in late game is rather frustrating at the moment. The main challenge is to catch a constantly retreating enemy force, before it can regain even the smallest amount of morale, and not to actually defeat your opponent on the battlefield.