Odessa is too hard. There's no natural boundaries to its north/west and there's 3 major roads M05, M15 and M16 leading from either western Ukraine or NATO countries.
Cutting from the Black Sea is not possible now, so Russia must focus on doing maximum damage and annexing maximum land up to defensible borders.
the whole campaign needed no less than double or even triple the number of Russian forces >300,000 men
the Russian intelligence was wrong to say that Ukrainians would welcome them as liberators
for this reason 120,000 were sent and they got bogged down, Russian are tough fighters no doubt but these are suicidal tactics by Russians
had they got the intel right they would cut off Western Ukraine with a entire Russian army of 100,000 men
this would stop the flow of weapons, then they would need over 200,000 for the rest of Ukraine
going in with 120,000 troops and allowing 1000s of ATGM and 1000s of MANPADS to enter from the West is basically a losing battle
unless those supplies lines are not cut Russia cannot win this war
you cannot take Ukraine without securing the Western border
they should now consolidate and hold