They don’t need to be.
Ukraine has no navy, no need for them to truly try to exercise power there.
Turkey not letting them through the bosporus doesn’t matter, they can blockade it from outside themselves.
But they do need a navy to protect critical infrastructure, and to launch missles, not to mention having any kind of deterrent to a near peer foe.
Every ship lost makes both less possible, as well as an embarrassment to the image they have projected for years
One of putins goals was to bring ussr er ah Russia back to the “we are important, and must be listened to” table
Every tank, aircraft, ship, air defense system lost degrades that, every drone or missile that gets through shows weakness .
Frankly don’t see many countries lining up to purchase weapons systems from Russia anytime soon even if they had systems to spare.
T-14 MIA,Su-57 mia t-90 destroyed in numbers, vaunted air defense systems destroyed by weapons they were supposed to be able to intercept.
Putin certainly has the resources to continue this for sometime, but at what cost for what benefit?