The main reason for the absence of medical evacuation is simple and gruesome: The fighting is just too intense.
It can take a day or even two for soldiers to get in and out of the fiercest fighting spots – killing any hopes of medics coming to save the wounded.
Left alone at the positions, the soldiers often have to pull out their comrades on their own under heavy shelling, sometimes walking five to seven kilometers to the nearest evacuation points, where vehicles take them to makeshift hospitals.
When soldiers carry their wounded out, the group is easy to spot – and it immediately becomes easy prey to Russian first-person view (FPV) drones and artillery.
War is, and has always been about logistics and material. Russia has China propping them up now. The west cannot send money to fight bombs. Ukrainian forces need air support and artillery shells, full stop.
Until the Ukrainian Forces get a substantial arms package, Russia will keep throwing unskilled bodies at Ukrainian trenches.
This is how Russian doctrine has always worked. Throw bodies at the problem until there are no more bodies. Encourage women to have more children. Rinse and repeat.