Hazama is using phenomenon Intervention to prevent Ragna from using the Azure since he's in control Takamagahara since the end of CS. Given that Ragna, at this point, possibly possess more than enough power to wipe out Hazama, it makes sense he'd go through measures to prevent him from using the Azure. It'd be kind of boring if Ragna just killed him outright.
And it's not like Ragna hasn't improved at all. He steamrolls over Tager(then again, this isn't much of a feat considering he's the series` resident jobber), Tsubaki, and holds his own against Hakumen, Nu, and Azreal(Keep in mind for the first two he needed to use the Azure to beat both of them, and for the latter he wasn't completely roflstomped like everyone else was before busting out the Azure.)