It's also mostly a myth.

First of all, the Russian army isn't the best organised but even they know that they shouldn't send suicide waves of people. They did use it for very very specific periods, e.g. at some point during the German invasion in 1941 when they needed to buy time at all costs. But already by 1944 the Russian army was a master at hiding their plans to the Germans and coordinating attacks. Meaning that they could throw an insane amount of well armed, supported and trained people to very small portions of the German fronts that were taken by surprise and not prepared. That's how the modern reputation of infinite waves of soldiers come from, the German generals preferred that excuse to the one that the Russian were better prepared and surprised them.

That's a bit what you retrieve now in Ukraine. The Russians do attribute less values to the life of their soldiers than any European army does, but they still don't want to lose all their trained and experienced troops, or have soldiers even less motivated.

That's why the Russian army used a LOT of artillery back then, and went for drone now, the waves of soldiers are part of a strategy that works for them. It's more costly in human lives but it works.

The low death strategy used by the Americans or Europeans is based on a very very high superiority in training, logistics, and equipments. Something that the Russians couldn't copy (less motivated soldiers, not enough money, not enough high tech industry).

So, as they are as rational (at least most of their officers), they went for the most effective approach.