The denial of sovereignty here is just a tool to achieve the goal Putin openly declared in particular in his editorial and speeches - erasing of Ukrainians national identity. In order to achieve that goal he kills and displaces carriers of that national and ethnic identity, ie. Ukrainians, and that is genocide.
"
In the present Convention, genocide means any of the following acts committed with intent to destroy, in whole or in part, a national, ethnical, racial or religious group, as such:
Killing members of the group;
Causing serious bodily or mental harm to members of the group;
Deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part;
"
Denial of sovereignty isn't genocide