If Ukraine gives up territory they have established that a large invasion will yield positive results, giving Russia an incentive to try again for more. Given that, in Ukraine’s position, what would you do? Choose to continue fighting, or choose to stop fighting now and then have to start fighting again in five years having given up loads of your ports and industrial base? You would need a guarantee that it would not happen.
What guarantee would you seek? The only one that makes sense to me is NATO membership, and that is exactly the situation Russia least wants to happen - they will not accept any deal in which Ukraine becomes a NATO member.
The reason for that is because more generally Russia wants to be able to threaten and conquer its neighbours at will. In other words, any attempt you make to guarantee Ukraine’s safety after a deal is struck is actually undermining Russia’s long-term goals and so will be refused. Russia only ever talked about negotiating to muddy the waters.
The only way to end the war favourably for the West and for democracies is for Russia to be defeated.