Lol you are just eating up Ukrainian propaganda. Of course the Russians are using its weaker outdated equipments/vehicles are on its first wave of attack not even their big toys yet and look how far they made it into kyiv still
Which academy of military science did you graduate from, West Point?
You obviously send in your very best right at the start of a war. You want it over with quickly. Why would anyone hold anything back in reserve? Big toys and crack units go right up first straight into the meat grinder, it's why you pay the big dollars for them. They're supposed to be on point duty.
You hold the garbage in reserve, the new recruits, the outdated equipment, so they can mop up whatever's left behind after your point men have forced an opening.
There is literally nobody stupid enough in the world to do it in reverse, send the garbage in first and save the best for last. That is simply the wrong way to prosecute a war.
Every hour that this war goes on, Russia's strategic outcome gets worse and worse. They needed to get this done as quickly as possible. Within 48 hours. Its dragged on for four days now and they're still a couple of weeks at least away from taking all the key cities in the country. Their advance has slowed to a crawl. This gives their enemies time to assist Ukraine. Time to marshal their forces together. Time to sanction and cripple Russia's economy. Time is the enemy for Russia. So it is utter madness to not have sent in your very best troops and equipment right at the start in the first push on day 1, hour 1.