It will be very difficult for the Ukrainians to retake the land bridge to Crimea, given their manpower disadvantage and the strength of the Russian defenses. Nevertheless, it has to be tried, because the benefits of success are immense. Ukraine would have more access to the Black Sea coast and would be in a position to attack Crimea at any time. Putin would see that the greatest prize of the war was in jeopardy; he might be inclined to negotiate to keep it. That could lead to a reasonable end to the war.
Using an attack on Crimea as diplomatic leverage is one thing; actually taking it would be something else entirely. It is not clear that America is willing to make enough of an investment in Ukraine to accomplish it. Neither is it obvious that the residents of Crimea, most of whom are ethnic Russians, would see the death and destruction that follows as “liberation.” Finally, Putin might be driven to escalate, either by using nukes or by attacking NATO supply lines, in an effort to keep his precious trophy on his bookshelf. In short, there are serious risks that may outweigh the rewards.
In my opinion, the best way to handle this is to go step by step. Try taking the land bridge, and if the Ukrainians succeed, see if Putin is then open to serious negotiations. If he is, great. If not, get ready for the next big offensive.