Those in the know will tell you the Ukrainian army is decimated. The Russians have totally wiped them out with very few remaining. They are so desperate for men that Poland forced Ukrainian men living there to go enlist in Ukraine.
Bear in mind Russia did all this using only Reserve fighters (doctors,dentists, teachers, welders etc) plus the Wagner Army for Hire.
They haven't actually deployed their real, properly trained soldiers.....
They are saving those for when they take down the US with China and North Korea helping.