The Russians clearly miscalculated the Ukrainian resistance to their initial invasion. If you look at their initial invasion thrusts, it was all along the border, and they tried to advance wherever they could. There was no concentration of forces or thinking of holding defensible lines. However, their situation is not totally lost. They are admitting their mistakes (at least internally) and withdrawing forces from hopeless fronts (such as Kiev) that are not central to the war at the moment. The Chernihiv and Sumy areas are also not that important. The main areas of importance are in the South and East.
On the Myoklaiv/Kherson front, the Dnieper gives both sides a natural defensive barrier. The Russians most natural course of action is to hold a perimeter around Kherson and the Dnieper but do not waste men and material trying to take Myoklaiv or advance to the West of the Dnieper. Their hopes of taking Odessa in the short run are nonexistent, but it is not that important as long as the port is blockaded.
The Kharkov front remains important (since losing badly there would cut off the Russian advance at Izyum, and by extension the Russian hopes of cutting off the Donbass grouping of the UA) and if the Russians start withdrawing from there, you know they've given up. I find this highly unlikely as Putin's domestic position would suffer a potentially fatal blow if he lost this war, after everything that has happened.
The Russians need more troops but they can still get that without conscription by increasing military spending and hiring more contract and volunteer soldiers. Yes, they will not be as well trained initially, but the Ukrainians don't have an unlimited supply of highly trained troops either. Russian industry would need to ramp up to produce more military equipment and they would have to find ways to do so without the supply of modern microelectronics that rely on the West. This is a major headache for Russia.
IMO for Russia, it's a good thing they are willing to recognize realities that the initial assault didn't work out and bite the bullet. While it's painful because the Kiev front was hard fought, it's better than continuing to spend men and material there with no hope of taking Kiev. I suppose you can say the front served a purpose in distracting the Ukrainians significantly for a month, even if that wasn't the initial purpose. If the Russians do persist and concentrate their firepower in the Donbass and Kharkov areas, they will be in a far better position tactically than they have in the last month. However in the long run their ability to draw up additional reinforcements from Russia itself and produce more weapons will decide the outcome of the war, provided that they have the will to wage it.