Russias not slowing down by choice, they want a quick end to the war.
As mentioned by HB, Russia could most definitely defeat Ukraine rather quickly like I incorrectly anticipated; however, in addition to the threat of having a failed state on the border, Russia would be risking the US empire and its proxy NATO finding lame psychotic excuses to intervene militarily leading to WWIII and the end of the World. That's why Russia has not bombed Kiev to the ground.
Russia and China for that matter do not want war, they and the rest of the BRICS nations want peace and trade. It is the US empire that wants war in a last-ditch effort to stop their ever-dwindling list of vassal states from joining the rest of the free World in BRICS; thus, putting the final nail in the coffin of their empire.
It's just their military is crap. Bad troops, equipment, training, command and control etc.
As for the Russian military being crap, what metrics are you using and who's reporting are you basing that assessment on? As of date, the once well-trained to NATO standards Ukrainian military has been all but annihilated so much so that they are lowering and raising the conscription age to find anybody to throw to the front lines. Moreover, there have been many experienced foreign troops including Americans that have been fighting and dying against the Russians and Ukraine is still losing.
Ukraine's military is pretty crappy too and they're just holding on because of the free stuff they're getting and the support from allied nations. The problem Ukraine has is equipment, ammunition, and training. is given to them very slowly, over months or years. And the restrictions that munitions couldn't be used inside of Russia made them fight with their hands tied behind their back.
As I mentioned before, the crappy Ukrainian forces you speak of are what they were left after their pre-conflict well NATO trained army was destroyed many months ago. Second, the fact you mentioned Ukraine not being given the supplies and armaments they desperately need indirectly contradicts your initial notion that the Russian military is crap. The military industries of Russia have proven far more capable than the US empire had anticipated. How can the Russian military be rubbish when they can not only maintain but grow their military forces to the size and logistical capacity it has now?
Seems like they're trying to get air superiority in the future by recently going after SAMs. To be more effective with rockets, drones, and cruise missiles now, and in a year or two to have fighers attack the front lines which they really need.
Everyone should pray for a quick end to this US imperial proxy war as all indications show that WWIII is on its way.