No doubt that, Russian stocks of low-tech ammo are enough to fight WW2 few times over, but they need to get them to the frontlines.
Currently Russian logistics is busy hauling vehicles, and heavier munitions, which can be launched from further away. That's logical.
Eventually, they will start going more towards tube artillery as their FOBs start running dry, but for tube arty the weapon/munition ratio is more important. Tube arty also needs way more trained artillery officers, whom they already lost a lot in Kiyv to counterbattery, and bombing
This is why we are seeing humongous amounts of 152mm SPGs being delivered from Russian reserves to the East. Russia has mostly abandoned 122mm calibre, unlike Ukraine.
The question is, whether they will make it in time. First Russian armour regiments are already trying to advance without long range support.
152mm range advantage will not matter much if they have to get up close to not to hit their own, or fire on entrenched positions.
155/152 advantage is mostly relevant in in offensive, when your armour can overrun enemy lines after the barrage, without letting enemy return long range fire, or in artillery duels with no own attacking forces close to the enemy.