I think that the lack of experience of Russians for ground combat is a significant thing though hence why calling on Wagner. Even those who have been in Syria, either as Russian soliders or via Wagner sound like they have little experience of ground combat either and seem to have largely ordered syrian milita (who perhaps crucially would know the area) and via air strikes.
If you read the stuff on Wagner operatives few actually sound that experienced when they start either. They are a ragtag bunch of drop outs and criminals with no morals who are looking for money. And theres examples of them not getting paid as they should too.
We know that the 400 deployed to Kyiv, have (so far) not been terribly successful. You have to assume that they were tasked to do things mainly during those first few days whilst the city was under curfew and many got 'dealt with' as a result.
Russia cant just train up new people. And neither can Wagner.
Moral and urban warfare is still in Ukraines favour. Comms issues still seem problematic for the Russians too.