Its fairly specifically about how systems (whether due to racist motivations in the past or not) can exist that produce race-biased results without active racism of current participants who perpetuate them, of any race.
While specific applications of its analytical framework to concrete conditions may identify contributions of active racism, past or present, CRT as a whole is a framework that divides individual racism as an active moral failing from societal processes that produce race-biased results and perpetuate pre-existing racial disadvantage.
The people criticizing it as “blaming White people” are actually afraid of the opposite, that it liberates White people to acknowledge structural racism without that requiring them to see themselves as active racists. As the critics very much do not want racist processes to be acknowledged and addressed (sometimes, because they are conscious, active racists, but sometimes just because their identity is tied up in the status quo being seen as free of racism or some other reason), they fear other people being made more free to acknowledge racist processes.