[Question] Is it definitely the case that we can colonize Mars if we really wanted to? Is it reasonable to believe that this is technically feasible for a reasonably advanced civilization?

Question phrased to say that I’m less interested in reasons why humanity might not colonize Mars in the short-term due to lack of interest, politics, or near-term economics. Assume that humanity really wanted to and would put billions or trillions of dollars towards this and decades (centuries) of time. Any real reason we couldn’t do it?