Ukraine loses most of its seacoast, from Mikolaiev to Mariupol. Thats a crippling and long term blow economically.
Status quo ante bellum might be acceptable, but that means the Russians have to leave a lot of territory.
They lost that coast after the 2014 coup decided to conduct ethnic cleansing and artillery attacks for 8 years against the Donbass. They really needed to get the Svoboda militias out of Kiev though. The last thing you need is a thug militia standing around watching you.
So now that coast is gone... forever.
“Status quo ante bellum might be acceptable, but that means the Russians have to leave a lot of territory.”
That would leave Crimea as part of Russia. I don’t like it, because it rewards Russian aggression (which began back in 2014), but it may be the eventual outcome.