Thinking Crimea will ever be returned to Ukraine is like expecting the southwest and California will be returned to Mexico.
Biden has already signaled to the Ukrainians that they're going to have to concede territory to Russia. All of the assistance coming from the US is designed to ensure Russia isn't able to advance too far into Western Ukraine not to take the fight directly to Russia. This assistance comes with strings attached, most importantly that the US has ultimate say over which targets Ukraine can go after using its systems.
Ukraine has given up Donetsk (hence the recent mandatory evacuation orders) and eastern Ukraine in general. It's no coincidence that this happened at the same time that the first grain shipments left Odesa. This was a behind the scenes quid pro quo.
They can't say this publicly but my guess is that at least in the south, the Ukrainians best case scenario is that the Dnipro River becomes a new UN managed demilitarized zone that serves as the de facto "border" between Ukraine/Russia. That's why Ukraine has been focusing on destroying bridges, rail lines, installations etc that supply Russian troops in Kherson using HIMARS. Unfortunately Russia has been moving all of its troops from the north and east to the south, especially around Kherson where Ukraine will concentrate its most recent offensive. They are dug into the city so all of the tech we've been sending to Ukraine isn't going to be as useful when it comes to house to house, street by street fighting. Russia has shown zero problems with simply bombing cities into rubble, civilians be damned. You also have the sunken cost issue where Russian power brokers, whether they support Putin personally or not, are unlikely to accept anything less than victory/control over eastern and southern ukraine considering what the army and economy has already gone through.