Russia is NOT all out against Ukraine.
Any country attacking another would in the start phase of war would.
1. Knock out the entire power grid
2. Knock out railway main bridges and road network
3. Water and sanitation
4. Constantly attack anything entering the country.
Why has Russia not done the above being so evil?
1. How and Why? How first, how do you knock out the entire Powergrid in Ukraine? In the old days, when we do it, we bomb the powerplant, it's a no go as Ukraine heavily rely on Nuclear Power. So the only thing you can do to take out the powergrid of THE ENTIRE COUNTRY is to taking out all the substation. You are talking about thousand if not tens of thousand of Substation. Are you going to knock all of them down? And then what if they repair some of them?
Are you going to knock them down with Missile or Air Strike? First of all, you need 2 or 3 missile per target to make sure they are destroyed. Or you fly deep into Ukraine and destroy them with your aircraft. Russia won't have enough missile to take them all out and flying aircraft only work in the East because if you go deep into target in Western Ukraine, you are flying over the entire length of a hostile facing mobile and static SAM and Air Opposition, in short, you are going to lose a lot of aircraft.
On the other hand, why? We are not in the 60s, let's say even if you can take out the entire grid, that probably will hinder Ukrainian industrial capability (which would alternatively be destroy if you target those instead) so are you saying Ukraine cannot fight at night without power??
2.) Again, how? That was a aerial intense task, let's pretend point 1 did not happen, you did not "waste" thousand of missile on their substation, how are you going to attack railway bridge and every road junction? First of all, it is not possible to do so with cruise missile, CEP is not enough and warhead is too small to make a different, which mean you are going to be looking at dropping a few snake on target if you want to destroy railway bridge or road junction. Then the same thing applies with point 1. You may be remotely able to do it in the East, but flying across the entire length of hostile country with Peer SAM system, sure, they don't have S-400. but S-300 would be more than a match for the Su-34 and Su-25 for that job. Even Stinger is enough to bring down (and they indeed brought down a few) those SUs.
On the other hand, Russia is a Armor heavy force, destroying the road would work against them because it will also slow their own advance.
3.) What does that do to Military? First of all, there aren't much to attack, you can't go after dams in Nova Karkova because it will flood Crimea, Ukraine don't depend on desalination plant. Which mean they can get water in numerous source, from rain water to truck them from Poland. This is more gear toward sapping Civilian morale than inhibiting Ukrainian warfighting capability, and that is assume you can do it anyway, the same things applies, you need to be able to reach that.
4.) How? What you can use to reach 500km inland from Belarus in Polish Border? You want to bomb them or you want to send missile? Cruise or Ballistic missile is for hard target, no one on this earth have that advance technology to target soft and moving target with Cruise missile. You want to fancy a long range ground strike day after day deep into Western Ukraine??
It's not about why they didn't do it, but whether or not they "can" do it.