You wrote something similar to me in regard to Odessa - as if a river is some mystical, inpenetrable barrier that can't be overcome.
Armies (and Navies and Air Forces) have breached/crossed rivers for thousands of years. This one has.
Not sure what ypu're thinking.
I've read about Russian logistics in this war. They suck.
With the use of satellites and drones, there's no way that the Russians can make it over to Odessa right now.
Kyiv? That's a different story.
If you're curious, Google "russian pontoon bridge".