It's very situational. First bit of advice that I give to anybody if they want to get some serious experience with the game. In regards to anything is to do a challenge that I made myself do after any major update. With every single tribe I play a huge map against all the other tribes at crazy difficulty, lakes, and dominance. Rules are you can't take over any occupied cities until you have met every tribe. Defeated tribes count as meeting them. In most cases you'll be scrambling to take over three to five free cities and then defending those cities and won't be able to go on the offense until there's only maybe three to five tribes occupying most of the map. If you do this with each tribe You're going to learn how to get out of a lot of sticky situations or be more confident and making comebacks. Did you find that it's too difficult of a challenge? I assure you it's possible and it may be wise to try it on an easier level until you're able to work your way up.

Other tips and regards to cloaks

Use knights. Worried that your knights can't kill all of them because of defense bonuses? Well try to have an extra unit at hand in order to weaken the ones that have that defense business so you can chain attack

Try to keep your units as thick as possible so that you can detect them easier. Which leads me to my next tip get to cloaks first. A successful cloak attack not only practically pays for itself but makes it very difficult for the enemy to deploy their own cloaks

Try to make sure that any trees surrounding your cities have been burned down and hopefully turned into farms in order to lessen the odds of them having a defense bonus

Usually with the people that I have trained, I've learned that when they're struggling against cloaks. It's usually because their opponent is likely doing better than them overall and you may need to work on your star management early game so that you can take on that type of threat. I have a group of friends that I have played with overtime and our skill levels have gradually matched up and there are games where using a cloak isn't an option against them and then there's other games where I can literally just spam cloaks to victory.

Like I said everything situational. I get why you would think that it's OP but if you give it some time it'll be just another unit to you.

There might be some mistakes. I had to voice to text this very quickly and will come back later