And it's not like the ships are badly designed. The Kuznetsov sister ship that was a casino for a while and now is Chinese works perfectly well. The problem with Russian navy is lack of maintenance, total disregard of safety and procedures, 0 fucks given about human life, uneducated, drunken crews and widespread corruption.
I recommend reading about K-429 - a nuclear submarine that sunk not once but twice. First time because it was ordered to do exercises while the hull was in maintenance. Despite protests of the crew. Second time in dock during repairs after it got recovered. Worker negligence apparently.
Fun fact - it's not the only Russian nuclear submarine that participated in 2 disasters.