To a certain extent, the answer to your question is fairly straightforward: Critical Race Theory (CRT) is a legal framework generally attributed to Derrick Bell, the first tenured African American professor of law at Harvard Law School. He, in collaboration with many other legal and social scholars, started to articulate the framework in the late 1970s, anchored in the ongoing work of civil rights activists who were looking to focus on laws as a driver for change as they felt the movement was losing momentum. Informed by the thinking of Critical Legal Studies, Bell approached the law with the understanding that laws aren't objective and neutral. Instead, they reflect the bias, prejudices, perspectives, and goals of the human beings who passed the laws and who are responsible for enforcing them.
It's helpful in the modern era to think of CRT as a field of legal scholarship that crosses different aspects of the law and serves as a way for legal scholars to think about the law, which in turn, informs how politicians and activists who study the scholarship think about the law and their efforts to change the law.
CRT, depending on which text one consults and when the text was written and who authored the piece, is generally recognized as having 5 to 7 tenets. (I'm familiar with CRT as it's used in education and around education law and am most familiar with the five as described by scholars such as Gloria Landson-Billings.) The five tenets can be summarized as^1:
The construct, firmly linked to the mental model that the law is not objective, was informed by the work of leaders in the feminist movement including scholars such as Barbara Smith (a founder of the Combahee River Collective who created the concept of "identity politics" to describe how the group of Black women advocate for social change based in their identity as Black women. She was also an editor on foundational text, All the Women Are White, All the Blacks Are Men, But Some of Us Are Brave which looks at how the law impacts women of color, especially Black women.) Kimberlé Crenshaw, also a legal scholar, would build upon Bell and Smith's work to develop the legal theory of "intersectionality" to describe the ways in which laws impact women of color, especially Black women.
Legal scholars and civil rights activists from other communities contributed to scholarship including Indigenous and Native, Hispanic and Latinx, and Asian scholars who focused on how the law impacts people with disabilities, and others. Mari J. Matsuda recently wrote about the origins of the theory in an essay called, Critical Race Theory is not Anti-Asian and laid out the early involvement of Asian American legal and social scholars in the work.
Finally, while there is no "opposite" to CRT as that's not how theories work, it can be helpful to think of CRT as a response to the idea of meritocracy, which is a sociological or political theory that claims people can rise (as it were) in a society based on their skill and aptitude alone.
1.Derrick Bell, CRT, and educational leadership 1995–present, Muhammad Khalifa, Christopher Dunbar & Ty-Ron Douglasb (2013) Race Ethnicity and Education, 16:4, 489-513
Critical Race Theory: An Annotated Bibliography, Delgado and Stefancic, Virginia Law Review Vol. 79, No. 2 (Mar., 1993), pp. 461-516 (56 pages), Virginia Law Review