People misunderstand Wagner’s role in the Ukrainian war.
Wagner is a prison to meat-grinder operation. Convicts were recruited, given a bit of training and sent on the most dangerous attacks. This meant that regular Russian troops were not expended, and that less civilians had to be drafted or recruited.
When Prigozhin complains about mistreatment, he’s probably right. To the Russian military, Wagner are useful, but scum. Remember that Prigozhin himself is an ex-convict, and he was sent to prison for theft, which included in one case choking a woman nearly to death.
Using convicts may have saved Russian troops, but convicts in the military never ends well. The same thing was done, without the mercenary cutout, in Afghanistan by the Russians and it did great damage to the Russian military.