[2021] Petro is Weak

I recommend the coming in to the forums and making a post asking for help with learning the ship rather than stating why it's bad.
Petropavlovsk has some of the strongest overall armor of any cruiser in the game. The 50mm upper hull and deck means that nearly all destroyer and cruiser HE shells shatter and do no damage. The placement of the hull low in the water means the citadel is extremely difficult to hit even when it is broadside to you. The AA is excellent. It has radar. It has Hydro. It has advanced penetration angles for it's AP shells. It has insane penetration values even at range.
It does many things REALLY well. It's extremely tanky and it's AP shells are lethal within 14km.

Primarily the extreme tankiness/low chance of punishing the ship are the biggest highlights. The addition of Radar and very potent AP are also large factors that must be considered.

If you want an actual conversation about the strengths of the ship, you can listen to a long form discussion here:

Direct Video Link: https://www.youtube.com/watch?v=G_6_DVXjV-4